Ocalarnd

If I may inject 2 cents worth, at least for your San Juan port of call. Arriving at 7AM and leaving early does present challenges for this port for activities. BUT there are two AWESOME old forts there, that are actually run by the US Parks Dept and are VERY cheap to enter and tour on your own ($5/adult gets you into both). It is actually a nice 20-30 minute walk up to Del Morro fort which is actually very nice in the early morning, and the self-guided tour routes, that you can easily find online, take you along the old City Wall, through the big old City Gate, and up the cobble-stoned roads through the old San Juan to experience the authentic old architecture, a couple OLD churches, and overall feel of the City. It is very safe, and you can save all that money for excursions at another port (or spend it on shopping and eating in Old San Juan). We actually took a taxi from Del Morro fort to San Cristobal fort, which was very cheap for family of 4, saved time and a nice ride. Ending at San Cristobal fort also puts you very close the cruise dock (5 min walk). Just beware that during the week the forts do not open until 10AM to start your inside self-guided tours (and there are no park service-led tours except on weekends), but that  also lets you catch breakfast before the start our. And the forts are so impressive. Also the bathrooms at the forts are VERY clean and air conditioned (the family appreciated that).
So consider some historical experience options for Old San Juan port. It will be a lot cheaper and keeps you close to the dock.
If you do choose to venture away on an excursion, I highly recommend an RCCL excursion at this port. The day we were there a RCCL excursion was late getting back to the ship due to San Juan traffic, but the ship remained at dock 20 minutes past departure, only because it was an RCCL tour.

Actually, we watched all the sales for 15 months before our Oasis cruise, for a deal on the soda package for the kids. Never saw any sale for the soda package. However, we were able to still buy it for $8.50/per person/per day (+ 18% gratuity) right as we walked onto the ship, on the promenade. So it can still be had for that rate onboard (at least as of June this year). Also we were able to apply our On Board Credits to the purchase that way.
Locate the various soda self-serve machines quickly once you board. They typically are only on the top decks and promenade (at least for Oasis class).

Your question regarding 5 yr old is prudent. We live in Florida and usually get annual passes most years. Starting from when our youngest was age 7. (Yes prior to that we did Disney, Sea World, and Legoland as great options)
Universal is a GREAT park(s) (better than Disney in my personal opinion). However, there will be much fewer things for the 5 yr old to do (specifically look at Universal Orlando's web page for height requirements). Universal Studios will have great simulator rides like Minions, and Shrek, and Transformers that he/she probably will be able to ride. And also the Woody Woodpecker kids coaster and the ET ride and possibly Men In Black (great family ride). Not to mention the animal stunt show and other "kids area" stuff. Lots of characters walking around as well. Not sure about the height requirement for the Diagon Alley ride (some rapid motion, short drops, and mostly 3-D story interaction). 
Islands of Adventure is probably not worth it for a 5 yr old. Much more focus on motion rides that have taller requirements. (But in my opinion the better Harry Potter area is still the Islands side, 2 coasters and the castle ride). Islands does have the great Dr Suess area for smaller kids, and there are some cool things in the Jurasic area (like the flying bird "swing" ride that is restricted to just smaller kids and their parents), and the Marvel comics area where you can sometimes get pictures with heroes and villans.  Again age 7-8 seems to be a great age to start here.
Beware, the parks are very crowded in the summer, and extremely hot & humid. Pace yourselves (build in sitting/rest times for the kiddos). Also, if you decide to do Universal parks on your own (apart from RCCL) I HIGHLY recommend you pay the extra $ to stay at either Hard Rock, Portafino, or Royal Pacific on-site hotels. Those hotels not only get you in and hr early each day to Harry Potter area, but also include FREE express passes for up to 5 people in a room, for each day (including check-in & out days). Those Express Passes easily double the rides you can cover in a limited time, and on a hot day, that means EVERYTHING.
Have fun & welcome to Florida.

We had a similar access problem. We received error messages about reservation access being unavailable, after our local (USA) travel agent major some changes in conjunction with RCCL that we requested.  Spent hours and numerous calls to RCCL phone #. They would say that they can "see it" and it should be accessible to me, and they "reset" it several times. Finally after several days and calls to RCCL and our agent, it was working again. I can't prove this, but I believe there was some issue with our agent not fully logging out or incorrectly disconnecting from our reservation, may have been the problem. Yes, we tried all the cache, history, and memory clearing on our end as well, to no avail.
So see if your US agent can open the reservation again, and then fully log out from it, and see if RCCL tech support can "reset" the access permissions.
Or yours may be an entirely new IT mystery (things can get blocked easily when the IP addresses of different countries and firewall rules get involved. Good Luck.

OK, I was the original poster for this inquiry, so I thought I would offer a short follow-up, since we ended doing it anyway.
Booked thru RCCL on a discounted sale promotion. So decent price. Very organized initial meeting at the pier by operators, then a 5 minute walk to the dock. The boat accommodates about 120 guests, and does have 2 bathroom (clean would be a relative term). Offered a non-alcoholic small cup of punch as boarding. Its about a 35-45 boat ride to the cove at the airport runway end. Anchor about 300 yds off shore and they tell you that you cannot set foot on the beach (I think this is to cover them from liability in case you do something stupid on the beach and get hurt by the aircraft jet/propeller blast. Did see several planes land while there (mostly turbo-props and smaller jets).
It has a floating dock attached to the boat that you can use for water entry/exit, or you can use the front ramp. But beware that trying to get back on to the boat via the ramp can take a LOT of effort, as the surf pushes you up, but then strong undertow pulls you back off. And there is the upper deck jumping off platform that the kids really liked.
Personally we found the visibility to be semi-clear. You could see about 20 feet down to the bottom, but not as clear as hoped. Very few fish, except for a few small ones that come around when they feed them with bread. Mostly sand bottom, but some basic flat rock formations as you get closer to the shore (or the bar area to the side).
There is really only 2 hrs on site, but actually that was fine with us, because the kids (ours were 11 - 14 range) were kinda losing interest by that point in the snorkeling. Also the surf seemed very difficult to swim against. Not high waves, just a lot of current. They did provide flotation "noodles" if you wanted, and they helped if you got tired from swimming.
There is a bar on the upper deck, and basic food can be ordered, but the prices really were not bad considering you are a captive audience for 3.5 hours. Tabs paid at end, but must be in cash.
So overall, personally, I would give it 4 out 5, IF you are looking for a sampling of snorkeling, combined with a decent water trip along part of the St. Maarten Dutch coastline. It left several hours to walk the shopping district afterwards. If you are expecting a hardcore snorkeling experience, then you want to pass on this one.

We just did the Oasis galley tour/brunch. It was offered to us while we were having breakfast in MDR (day 6). They included free Solarium specialty dinner that nite, and the tour the next morning. 
Mimosas, champagne, or OJ before tour. Tour gives idea just how big the food staff is. Meet the main chefs, can ask questions. Fairly interesting. Brunch had a number of very good menu options and they encouraged ordering multiple items. So worth it one time, for us. 

We just did the Oasis galley tour/brunch. It was offered to us while we were having breakfast in MDR (day 6). They included free Solarium specialty dinner that nite, and the tour the next morning. 
Mimosas, champagne, or OJ before tour. Tour gives idea just how big the food staff is. Meet the main chefs, can ask questions. Fairly interesting. Brunch had a number of very good menu options and they encouraged ordering multiple items. So worth it one time, for us. 

OK, I was the original poster for this inquiry, so I thought I would offer a short follow-up, since we ended doing it anyway.
Booked thru RCCL on a discounted sale promotion. So decent price. Very organized initial meeting at the pier by operators, then a 5 minute walk to the dock. The boat accommodates about 120 guests, and does have 2 bathroom (clean would be a relative term). Offered a non-alcoholic small cup of punch as boarding. Its about a 35-45 boat ride to the cove at the airport runway end. Anchor about 300 yds off shore and they tell you that you cannot set foot on the beach (I think this is to cover them from liability in case you do something stupid on the beach and get hurt by the aircraft jet/propeller blast. Did see several planes land while there (mostly turbo-props and smaller jets).
It has a floating dock attached to the boat that you can use for water entry/exit, or you can use the front ramp. But beware that trying to get back on to the boat via the ramp can take a LOT of effort, as the surf pushes you up, but then strong undertow pulls you back off. And there is the upper deck jumping off platform that the kids really liked.
Personally we found the visibility to be semi-clear. You could see about 20 feet down to the bottom, but not as clear as hoped. Very few fish, except for a few small ones that come around when they feed them with bread. Mostly sand bottom, but some basic flat rock formations as you get closer to the shore (or the bar area to the side).
There is really only 2 hrs on site, but actually that was fine with us, because the kids (ours were 11 - 14 range) were kinda losing interest by that point in the snorkeling. Also the surf seemed very difficult to swim against. Not high waves, just a lot of current. They did provide flotation "noodles" if you wanted, and they helped if you got tired from swimming.
There is a bar on the upper deck, and basic food can be ordered, but the prices really were not bad considering you are a captive audience for 3.5 hours. Tabs paid at end, but must be in cash.
So overall, personally, I would give it 4 out 5, IF you are looking for a sampling of snorkeling, combined with a decent water trip along part of the St. Maarten Dutch coastline. It left several hours to walk the shopping district afterwards. If you are expecting a hardcore snorkeling experience, then you want to pass on this one.

We just got back, and did the Galley Tour on the Oasis. It was fairly interesting (ours was of the Deck-4 Main Dining galley). Our 12 & 14 daughters went along and found it to be OK. The brunch at the end was actually VERY good.
But you might want to wait until getting on the cruise. They came by our MDR table on Day 6 at lunch and offered it to us for Day 7, but also included dinner that night (Day 6) in the Solarium Bistro (which was GREAT), for $35/person. So, that seemed decent for tour, brunch, and specialty dinner.  Not sure if that offer that deal on every trip.

We just got back from our Oasis cruise, with Labadee stop.
Direct answer: You "sign-in" at a hut near Adreneline Beach next to one of the lunch serving buildings. Then very short walk to bottom of the coaster. The entrance & exit are right next to each other. You climb in a car, sit through a short 30 sec ride safety video (probably 4 or 5 times as your car moves to the starting point). Then it pulls you via cable up to the top of the hill, where it starts downhill. They require you keep both hands on the break levers (you have to push them forward to go forward and pull back to slow or break), but I was able to hold a GoPRO stick in right hand and still keep hand on the lever.
I am almost 50, and very overweight, but I was still able to get in the car will out much problem, and to my surprise the seatbelt actually was able to come across and buckle without any extension. The ride itself is not very fast or physically taxing at all. In fact you will probably have to slow down because of others taking a more leisurely speed down the tracks anyway (but several GREAT views looking out from the hillside.
Are you in Ocala, FL?

Just got off Oasis. Had an outside balcony cabin.
Power strip: We took one of those basic white or brown interior extension cables (with the 3-plug junction on the end, but no surge suppression). There was a plug on the wall, at almost floor level, right behind the bed frame (bed moved easily to access it). Used it to plug in C-Pap machine, phone charger, and one of those black mini-huricane fans (gotta have that air movement at night).  Set everything on the little table (usually in front of couch) and slept like a baby.
Magnets: Choose your magnets CAREFULLY. All of the magnet hooks have much LESS holding strength than advertised when they are mounted to a wall and the weight is pulling down (shearing force). We took 60 & 80 lbs versions and they were able to hold hangers with wet towels & bathing suits (we took about 8 magnets per cabin). They are a GREAT idea, but be careful where you pack them, because they can "erase" phones, tablets, laptops, or any other electronic memory.
Also we used a small magnet on the door of the closet safe, to pull it open/close. Otherwise, ours did not have any other "handle" to open it. The safe it good size and very easy to use.
Someone earlier (another post) made great suggestion to use clear packing tape to keep all lotions & liquids items closed. My follow-up reminder is to bring something to cut the tape off (scissors smaller than 4"). Nail file will work, but its a pain.
We took small night lights to plug into desk outlet. And they provided just enough light to make the nite time bathroom calls easy and pain-free.
 

Just got off Oasis. Had an outside balcony cabin.
Power strip: We took one of those basic white or brown interior extension cables (with the 3-plug junction on the end, but no surge suppression). There was a plug on the wall, at almost floor level, right behind the bed frame (bed moved easily to access it). Used it to plug in C-Pap machine, phone charger, and one of those black mini-huricane fans (gotta have that air movement at night).  Set everything on the little table (usually in front of couch) and slept like a baby.
Magnets: Choose your magnets CAREFULLY. All of the magnet hooks have much LESS holding strength than advertised when they are mounted to a wall and the weight is pulling down (shearing force). We took 60 & 80 lbs versions and they were able to hold hangers with wet towels & bathing suits (we took about 8 magnets per cabin). They are a GREAT idea, but be careful where you pack them, because they can "erase" phones, tablets, laptops, or any other electronic memory.
Also we used a small magnet on the door of the closet safe, to pull it open/close. Otherwise, ours did not have any other "handle" to open it. The safe it good size and very easy to use.
Someone earlier (another post) made great suggestion to use clear packing tape to keep all lotions & liquids items closed. My follow-up reminder is to bring something to cut the tape off (scissors smaller than 4"). Nail file will work, but its a pain.
We took small night lights to plug into desk outlet. And they provided just enough light to make the nite time bathroom calls easy and pain-free.
 

We just got back from our Oasis cruise, with Labadee stop.
Direct answer: You "sign-in" at a hut near Adreneline Beach next to one of the lunch serving buildings. Then very short walk to bottom of the coaster. The entrance & exit are right next to each other. You climb in a car, sit through a short 30 sec ride safety video (probably 4 or 5 times as your car moves to the starting point). Then it pulls you via cable up to the top of the hill, where it starts downhill. They require you keep both hands on the break levers (you have to push them forward to go forward and pull back to slow or break), but I was able to hold a GoPRO stick in right hand and still keep hand on the lever.
I am almost 50, and very overweight, but I was still able to get in the car will out much problem, and to my surprise the seatbelt actually was able to come across and buckle without any extension. The ride itself is not very fast or physically taxing at all. In fact you will probably have to slow down because of others taking a more leisurely speed down the tracks anyway (but several GREAT views looking out from the hillside.
Are you in Ocala, FL?

Thank you to so many of you that shared here. You really helped with our first-time cruise experience on Oasis.
With that said, I will try to add constructive comments where I can, to assist others. So please don't beat me up for sharing a couple areas that I think folks should be aware of before their first cruise (yes, I have shared these comments with RCCL on the survey).
Soda package/machines: The coke self-serve machines are a GREAT idea, but I just don't think RCCL has adequately addressed their short comings or potential. We experienced extreme frustration, especially on the 1st day, trying to locate available machines, and trying to get product out of them. 1) There are not enough of them. We counted only 7 or 8 of them on a ship with 6,000 passengers. 2) FREQUENTLY they were out of ice (these machines have to be manually restocked with ice by the crew), 3) There were many times that the machines ran out of soda (particularly diet sodas), were inoperable due to be in "maintenance mode". Yes, you can still get soda at most bars, but not the same level of selections, and also with additional waiting. Again, this a great idea with huge potential for enhancing the enjoyment and efficiency of the cruise beverage experience, It just hasn't been adequately deployed in my opinion. There should be at least 1 of these machines on EVERY deck level (including the cabin areas).
Featured Activity Venues: Yes, Oasis has 2 really cool Flowriders, but unless you pay for semi-private assigned lesson time, or are willing to stand on the burning deck for hours waiting, you probably will not get to actually use them. The open-use time is too limited to accommodate the volume of cruises that would like to try them. Again 6,000+ passengers, with approx 1,000 kids/teens (not including interested adults wanting to give it a try), and 2 Flow-riders, with limited open-use hours. Similar circumstance for the 2 Rock walls. There are 3 or 4 rope lines per wall, so it does move a bit faster, but again high demand vs. limited availability, you better set aside an hour or two if it's on your must-do list. I will say the Zip-line was more available and less waiting than I expected. Ice skating was the other area with very limited open-access times and limited opportunities (but the Ice Show was GREAT).
Shows: Come Fly With Me - Great performers, singing, and entertaining, especially for kids/teens. Headliner was "Mo5aic" - AWESOME performance, very much like Pentatonix (they will be on several upcoming Anthem cruises per their website). "Frozen In Time" Ice Show - VERY Good (this is not "Frozen", but a collection of stories on Ice). Get there early and try for first 4 rows. "Cats" - Very good performers, singers, dancers, and technical production. But the story line is very boring (over half the audience did not come back after intermission). Aqua Show - Good, but cheesy at times. Very good trampoline stunts, and decent diving (especially for a small pool on a moving ship).
Eating: MDR was GREAT. Wipe Out Cafe & Solarium Bistro are both great options especially for breakfast, Windjammer was a disappointment. It basically was Golden Corral Buffet dining, but not as good. The food was very mediocre (hamburger was one of the better items) and the desserts were surprisingly "bland" and disappointing. The MDR offered a very good lunch buffet, so stick with that, unless you are hanging out poolside all day.
I know its a lot, but this is stuff that we wanted to know before our first cruise. Hope it helps someone with their planning.

Great link/reference. Thanks a bunch.
 
Any insider tips for visiting the forts (we are middle aged parents with teens)? My concern is that I have read that the offered excursions, really don't provide much actual time at the forts, and don't do many other "stops" for pictures or looking around.

Looks like Pier 3 as it was specifically expanded to accommodate the ship.
 
http://caribbeanbusiness.com/puerto-rico-to-welcome-one-of-worlds-largest-cruise-ships/