You will have plenty to do onboard the Enchantment OTS. First, while onboard always refer to her as a "ship", never a "boat".
In Cozumel, a great trip is to the Mayan ruins in Tulum. Take the ships tour, since the tour includes a ferry trip from Cozumel over to Playa del Carmen and a bus trip, trying to do this on your own would be extremely difficult. The ship's tour will come with an english speaking guide and include the entrance fee to the ruins. In Belize, visit the zoo or one of the bird sanctuaries there. Be very careful with wondering around Belize City, many neighborhoods are NOT safe for tourist. There is a tourist zone at the dock where your tender will bring you into, if leaving the tourist zone, use one of the tourist taxis rather than try to walk. You are perfectly safe in the tourist zone which includes activities, restaurants and shops. When I was in Belize, we did the cave tubing in the jungle and had a great time.
As for the ship, the Enchantment OTS is a Vision Class ship and doesn't have all the bells and whistles of the Voyager or Freedom class ships. It has very nice public areas, including a shopping area, a library, internet cafe, pool deck, many fabulous lounges, a rock climbing wall and so on. She doesn't have the Royal Promenade, the ice rink, or flow riders, but she still has great public areas, spacious rooms and great activities. Read the Cruise Compass every day to get a good idea of the daily activities. A few years ago, they did add a new section to the middle of the ship and lengthen her adding new cabins and more public areas.
The dining room is a multi-level dining room and you will have the same table every evening. The dining room has different sections and each level is a different dining room. You'll have the same wait staff every evening, and the table sizes range from 2 - 12 per table. Nothing to dread, just show up and enjoy the food. You also have the option of the Windjammer cafe which is the buffet onboard.
Enjoy and have a great cruise!