ScooterScott22

The first message is specific to your cruise so not really a mixed message.  That is the one that you need to utilize as the "truth".  You should still try to be there around your specified boarding time, taking into account any possible delays.  I'm sure there will be some leeway accommodated in actual boarding time. 
The second message is standard message that goes out to everyone for every cruise.  They are trying to avoid having people show up early just to get on the ship which will create issues like the lines pictured below for entrance to the terminal.

From a sign in Cunard, the "fancy" dress was not only for esthetics but for practical reasons if you went overboard.

Reconciling these two seemingly conflicting messages together, they're saying, "With the potential disruptions and delays due to the NYC Marathon, plan to make it on time for your designated Port Arrival Time."

The first message is specific to your cruise so not really a mixed message.  That is the one that you need to utilize as the "truth".  You should still try to be there around your specified boarding time, taking into account any possible delays.  I'm sure there will be some leeway accommodated in actual boarding time. 
The second message is standard message that goes out to everyone for every cruise.  They are trying to avoid having people show up early just to get on the ship which will create issues like the lines pictured below for entrance to the terminal.

Yes, it would be a good idea to go to the MDR at some point, early in the cruise, and let them know that you will not be coming to the MDR.  I have read that the maitre 'd at the MDR console can "see" that you have dining reservations elsewhere, but I have been told BY the maitre 'd that the MDR database is not the same as the specialty dining DB and that they canNOT see the specialty reservations....so not sure which is true.  It can't hurt to drop by and tell them...then your conscience is clear for the remainder of the cruise !!

It shows available for our sailing in 3 days.

Last month while boarding we did not meet the genie until the boarding.  There are multiple steps that might interrupt your plans.  
Not sure what port you are embarking but at Ft Lauderdale there is a Star banner and a host to take your name and initial check in, a porter will come for the bags and a “shoreside genie” will take you to security and to the check in, then they took us to the lounge to wait while the genie came to take us on the ship.
Not sure that the shoreside staff will be as accommodating as the genie.  Pretty sure they are going to be a little more by the book.

We’ve always referred to these events as the “cattle call”.  Complete waste of time, IMO.

Chef's Table is a fantastic time: equal parts food, wine, and social experience with the other foodies around you.
A few considerations:
Select an evening where you can devote 3 hours to this meal. Don't pick an evening that has activities you want to go to (headliner show, Love & Marriage show, comedian, etc). You're going to miss those activities because you'll still be at Chef's Table.   Other evenings you'll be going to the Main Dining Room. If you haven't yet download the Royal Caribbean app, do so now, select your cruise, go to Dining, then Main Dining Room. You can browse the rotating menus, and go to Chef's Table on a night where the Main Dining Room food doesn't interest you as much.  Some minor points on each day:  Day 1: May not be the best idea - you'll will be busy, and you'll want to decompress and just enjoy the ship.  Day 2:  May be good, as a positive experience at Chef's Table will put you in good spirits for the rest of your cruise Day 3: If you're planning on an intense day in Cozumel, make sure you can get back in time to shower, change, and arrive for the start of your meal Day 4: If you can get fully packed and ready to walk off the ship the next morning PRIOR to your Chef's Table start time, this would work as well.  

I would go with anytime including as early as possible.  The only thing to consider here is traffic and it could be heavy heading into Miami in the morning but still shouldn’t be so horrible that you could be on the ship by 11 to 12 o’clock.

+1 on this. 

I agree with @ScooterScott22.  I think your idea of having your mother in a separate room is a good plan and I believe it will work well for you.
Here is what she will NOT be eligible for:
1.  Visiting the suites lounge, the Coastal Kitchen or the suites sun deck
2.  Unlimited dining outside of the suite (unless you purchase the UDP for her) or free drinks outside of the suite (unless she gets a drink package).
3.  Technically, she is not eligible for reserved seating in theater venues however, I have never had a Genie fail to include a limited number of non-SC guests to our reserved seating requests.  This is really a Genie-specific thing....could they technically refuse to seat your mother with the rest of the family ?  Yes....but would they ? No....especially since it's just 1 person.
As for eating and drinking in the suite, as others have mentioned, it is basically unlimited food and drink (except for liquor and wine) to whomever wants it.  If your mother wants Starbuck's delivered for her along with everyone else's morning drinks, that will be no problem....just know that it will only be delivered to your suite, so she would have to come and fetch it and either drink it in your suite or take it back to her room.  It will not be a problem.  Same with any food delivered to your suite.  They neither know nor care who is eating or drinking in your suite.  They do not "count" so if you order 5 Starbucks every morning for a suite with only 4 people in it....nobody cares.
Here is what I would recommend:
1.  Purchase the UDP for her.  That way, she can join you for any meal, at any time as long as it is not in the Coastal Kitchen. ...and OBTW, if you don't want to miss filet night in the CK (usually night #1 but could be any night) just have it delivered to your suite and she can have one with you, if she wants !!!
2.  If she wants to have unlimited drinks outside of your suite, then purchase her a drink package. If she is a liquor or wine drinker, then you will need the UDP but if she only really cares about non-alcoholic beverages (water, soda, coffee, fresh squeezed juice, etc.), then the refreshment package would work.  You will be able to order liquor/wine-by-the-drink for her, to be delivered to your suite any time.  Same with Starbuck's.
Enjoy the GLS.

🤣🤣🤣 You forgot to include "a safe for you laptop" and so much closet space"!!!
The videos are great and we love him too.
Have fun sailing!  We just did the Royal Loft on Allure and have a 2BR ATS in the future so we will be following.

I'll chime in since we had the GLS on the starboard side (10720) for an Alaska sailing (Ovation) a few years ago.  
We really enjoyed the stateroom.  Granted we had not done one of the larger GLS before so we did not have any perspective one how much space we could have had with the middle versions.  Space was never an issue for our party of three, since we would most commonly cruise in a regular veranda stateroom this room was nicer.  Our son did have to use the downstairs and the closet down there.  As far as noise, the was some noise from the Owners Loft Suite below just after boarding as the group opened their champagne to toast.  Otherwise it was really quiet the while time.   
What we did like was having the extra veranda's for Alaska.  Being able to get outside to look at wildlife or the scenery from the side or back and even the upstairs bedroom was nice.  With that sailing there is almost always something to see out there and you neve know when something interesting might show up (whales, seals and eagles) that you want to get outside quickly for.  
We did have one of the center GLS on deck 8 booked for sailing that was cancelled so can't give a direct comparison. 
Have fun, no  matter where you end up!

I'll chime in since we had the GLS on the starboard side (10720) for an Alaska sailing (Ovation) a few years ago.  
We really enjoyed the stateroom.  Granted we had not done one of the larger GLS before so we did not have any perspective one how much space we could have had with the middle versions.  Space was never an issue for our party of three, since we would most commonly cruise in a regular veranda stateroom this room was nicer.  Our son did have to use the downstairs and the closet down there.  As far as noise, the was some noise from the Owners Loft Suite below just after boarding as the group opened their champagne to toast.  Otherwise it was really quiet the while time.   
What we did like was having the extra veranda's for Alaska.  Being able to get outside to look at wildlife or the scenery from the side or back and even the upstairs bedroom was nice.  With that sailing there is almost always something to see out there and you neve know when something interesting might show up (whales, seals and eagles) that you want to get outside quickly for.  
We did have one of the center GLS on deck 8 booked for sailing that was cancelled so can't give a direct comparison. 
Have fun, no  matter where you end up!

Just being realistic to help manage expectations - Suites, Pinnacle and The Key will all be allowed into the terminal first.  Those same groups will be the first to board, after the back to back cruisers are cleared and boarded (if they come off the ship at your port).  Clearing the ship and inspections can also cause delays to the boarding process.  
I'm not saying you cannot try to get the most of your day by attempting to be as early as possible, but stick relatively close to your check-in/boarding time for the best process.  It could be disappointing to find that your port is adhering to check-in times and you have to wait.  Even if you have an earlier check-in and you show up at 9 am, it would not be fun to start vacation only to find that your stuck waiting to get in until those other groups are allowed in, and then stuck sitting in the holding area until those other groups board.  It may go relatively fast but can seem like forever.

Agree with the suggestion above to put some of the party into another transport.  The process @BethW mentioned is feasible but is that really what you want to do? 
Drop off will not be an issue, and returning to the hotel is not much of a time loss but both trips into the port area could encounter some traffic/delays. The major factor is those waiting at the port.  The folks waiting at the hotel for the second trip, while the first group is dropped, will not have any issue.  Those at the port are sort of stuck in limbo while waiting for the second group. 
Not sure how the reservations are setup across the group but if the right parties are together, the first group certainly could go through the check in process and everyone meet up on the ship.  Is that what you wanted? 
If you wanted the group together for the whole boarding process, there really is not a great spot for the first group to wait for the second group.  There is an upstairs hall that the first group could sit at while waiting for the second group.  They would go through security and the check-in and just wait there before boarding. 
There are a few potential things to consider if boarding in two separate groups.  First is that OK with the whole group or did you want to be all together through out the process?  Second, there is a boarding photo opportunity.  Would you even want a boarding photo and if so do you want one of the whole group together?  And finally, easier to manage, but will all the right people be in all the right places for check-in/boarding in the two group scenario.  If any bags, people or paperwork are not in the right bunch, it can be worked out but may not be as easy as the one group scenario.

Agree with the suggestion above to put some of the party into another transport.  The process @BethW mentioned is feasible but is that really what you want to do? 
Drop off will not be an issue, and returning to the hotel is not much of a time loss but both trips into the port area could encounter some traffic/delays. The major factor is those waiting at the port.  The folks waiting at the hotel for the second trip, while the first group is dropped, will not have any issue.  Those at the port are sort of stuck in limbo while waiting for the second group. 
Not sure how the reservations are setup across the group but if the right parties are together, the first group certainly could go through the check in process and everyone meet up on the ship.  Is that what you wanted? 
If you wanted the group together for the whole boarding process, there really is not a great spot for the first group to wait for the second group.  There is an upstairs hall that the first group could sit at while waiting for the second group.  They would go through security and the check-in and just wait there before boarding. 
There are a few potential things to consider if boarding in two separate groups.  First is that OK with the whole group or did you want to be all together through out the process?  Second, there is a boarding photo opportunity.  Would you even want a boarding photo and if so do you want one of the whole group together?  And finally, easier to manage, but will all the right people be in all the right places for check-in/boarding in the two group scenario.  If any bags, people or paperwork are not in the right bunch, it can be worked out but may not be as easy as the one group scenario.

Expect that it is horrible in February.  It gets so cold here in Florida that during most of February our AC is actually turned off. 🥶

Normally it would, but you know what I'm talking about. I ran into Publix yesterday morning in shorts and a t-shirt... I saw winter coats! 🤣

Expect that it is horrible in February.  It gets so cold here in Florida that during most of February our AC is actually turned off. 🥶

Expect that it is horrible in February.  It gets so cold here in Florida that during most of February our AC is actually turned off. 🥶

Expect that it is horrible in February.  It gets so cold here in Florida that during most of February our AC is actually turned off. 🥶

Not all places will do this for cruise visitors.  I asked while we were in Curaçao and couldn't find anyone that knew of a place to get a stamp.  There were a few places we inquired in the past, like Cartegena, that did not have a place that was available since they clear the whole ship in one process.  There are others that were quite accommodating.  While transiting the canal, a Panamanian immigration officer came onboard and was available at guest services to provide passport stamps.
It also gives you another reason to have your passport with you when you leave the ship while in port.

Not all places will do this for cruise visitors.  I asked while we were in Curaçao and couldn't find anyone that knew of a place to get a stamp.  There were a few places we inquired in the past, like Cartegena, that did not have a place that was available since they clear the whole ship in one process.  There are others that were quite accommodating.  While transiting the canal, a Panamanian immigration officer came onboard and was available at guest services to provide passport stamps.
It also gives you another reason to have your passport with you when you leave the ship while in port.