xchellz

There will almost always be a place to lock your belongings up.  I did the parasailing on Labadee, they have lockers to rent on the island.  I actually did the zipline and parasailing.  I rented the locker for the zipline and could have kept it for the remainder of the day but I just gathered my backpack after the zipline and carried it around with me.  While on the parasailing tour, I and several others left our backpacks on the boat.  There was 8-12 people on the boat and two at any time would get on the parasail.  They had us move around the boat as two came back on two were getting ready to sail.  I actually gave my camera to the tour operator to take photos of us while we were up there.
The cruise compass will post what is required to get back on the ship (usually your sea pass and a photo ID).  If a passport is required to reboard they will let you know in the cruise compass and will be posted as you leave the gangway.  
In most cases whether you have your passport or not when going ashore is a matter of personal choice and comfort level.

For ziplining in Haiti, you can rent a locker for $8......
 
If I had to do it again, I would have just left our stuff on a beach chair to be honest...
 
Cant speak for the other tours you're doing..

Thank you all! I decided to book a tour with RC!

Thank you all! I decided to book a tour with RC!

Thank you all! I decided to book a tour with RC!

Concur with @WAAAYTOOO , and there was the recent sad story about Carnival passengers in Belize who had a terrible bus crash with a 3rd party vendor.  No one is immune from an accident, but supposedly Royal vets their contractors.
If you get to Costa Maya, don't overlook the Chacchoben excursion that Royal offers -- no ferry ride needed!

I have heard that the hibachi can fill up quickly due to the limited seating for each timeslot so that one I would recommend booking ahead of time. 

Yes, if you really want the Hibachi reserve it ahead of time. On our recent sailing they turned people away all week, it is really a tiny space on the Harmony. The concierge mentioned the demand was high and the availability zero. There were 10 seats to a Hibachi (really tight) and I believe 3 separate Hibachi grills. It was crazy loud as for the most part everything is timed really close together so lots of people and the chefs were all speaking their narration pretty loudly. For the meal plans they explained unless you were Star class and/or paying al la carte you were given a 35.00 credit for the seating for each person dining. The meals were $45.00 & $49.00 and then if you wish there were many add on menu items, example soup (not included) It was an okay experience for us but we were quite underwhelmed. I think they may have added a seating due to demand because we were told 1730hrs initially but then contacted on the ship and told 1700hrs instead for start time. Hope this helps, Happy sailing you will LOVE it!

@xchellz you can always just pay for Hibachi one night and get 2 for 1, pr 3 night package.  We did UDP but our ship did not have Hibachi. It was our first time on RCCL so we got the UDP to avoid loud restaurants.
if you do UDP some ships are offering Hibachi as part of the package now. See
 

Reservations for specialty restaurants are recommended but not always required -- it depends upon the time.  At peak times they might not be able to accommodate you. We make reservations on the ship after we have checked show times and other events on the Cruise Compass.  I am not sure which ship you'll be on, which affects your choices.  We liked the Central Park 150 on the Harmony for a romantic dinner.  They also have Izumi.   By the way, the Main Dining Room is nice, although more crowded than a specialty restaurant.  If you look up the deck plans for your ship, you can locate restaurants.https://www.royalcaribbean.com/cruise-ships/deck-plans

Thanks! I had no idea. I am missing the perks already but still looking forward to my view.

I assume that the Perks you are referring to are ones that come as part of staying in the Central Park Balcony room rather than perks that would have offered as part of the booking in general.
These Perks are associated with the room type, its to give a bit more of an intensive to purchase in "internal balcony" on the Oasis class of ships
As you are no longer staying in this type of room these perks would then be given to the person(s) that would now be booked into the Central Park Balcony room you vacated.

Sorry.. You lost those Perks when you upgraded to a different category..  You will have a great view of the ocean though