I did something similar to your cruise, but not Roatin.
Belize was my absolute favorite.
First, don't go with the tours through the ship. But, check out the reviews for the other tour companies. I got all my great information for joining www.cruisecritic.com
. They have boards just like this one and you can join, find others that are going on the same cruise as you and find reviews on all sorts of cruise excursions.
In Belize, I hired a private trour guy that gave us the zip line and cave tubing. We got a tour of the city of Belize and still had time to do shopping. I loved getting out and meeting the locas. That's my favorite thing to do.
In Cozumel, well, lets just say I only remember arriving there.
We took the booze cruise, went out and did snorkeling, went to a private club and then came back and got trashed at Senor Frogs. A day to forget!
Very touristy so that's why we chose to do those 'touristy' things.
In the Caymans we took a tour on jet ski's out to the swim with the sting rays then out to a island area where we hung out on the beach and drank at the beach bar. It was a lot of fun!! Loved the Caymans but didn't have enough time there.
I also went Parasailing at Costa Maya. Didn't like the town (it's only a cruise ship town) but had a great time parasailing.
Again, my biggest suggestion is to go to cruisecritic.com and get all your info and reviews there. I'd be glad to pass along the information to the guy who gave us the private tours in Belize. Shoot me a pm if interested!!
Alcoholic beverages are NOT included with costs. We wrapped a couple of bottles of alcohol up in towels and shoved them in our suitecases. The require you to lock your suitcases before you check them with the port, so you shouldn't have a problem. But, again, that was a couple of years ago. Also, take a couple of larger cups to use on the ship and carry around with you. You can put your alcohol in your cups and fill them with whatever juices or sodas you want in the cafeterias.
Definitely plan to do at least one night of the formal dinner. It's great! Take time to get to know others at your table. It's fun to make friends on the ship. I still keep in touch with some of those we met on our cruise several years ago.
Make sure to check out the Carnival Capers each day. There's all sorts of fun events to do.