Hi Veronica, and welcome to Cruise Chat!
Congratulations on going on your first cruise. You can expect to get hooked on cruising! You're all going to have a great time. Going with friends is a lot of fun.
I'm not going on your cruise, but have cruised on Majesty of the Seas several times. It's a great ship, even better now since its recent refurbishment and renovation.
Contact the travel agent who booked your cruises, and tell him/her that you and your traveling companions want to eat together, and which seating (Main or Second) you prefer. The agent should call Royal Caribbean, move one couple to the other seating, and make sure Royal Caribbean has your booking numbers cross referenced, so that you're put at the same table. Also, you can request a table for 4, 6 or 8 people. While it's just a request, you may as well note your preference and Royal Caribbean will try to get you at your preferred table size.
In Nassau, it really depends on what you like to do. You can see the shore excursions that are offered, if you go to Royal Caribbean's web site
, click on "Before You Board" and then "Land and Shore Excursions." The last few times I was in Nassau, I just walked around town, poking into stores, looking through the Straw Market, etc. You can take a water taxi to Paradise Island, or take a shore excursion to see the big Atlantis Hotel. Lots of different things from which to choose, or do your own thing.
I would arrive at the pier by about 12:30pm on Monday. As soon as the ship has been cleared from the previous cruise, they'll start letting people on the ship, and that's really when your vacation starts.
Have a great time, and do come back and tell us how you enjoyed it.