In St. Maarten, just catching a cab and going to one of the beaches is fun. We went to Orient Beach (French side, possible toppless and nudity). The beach was wonderful. The water great. If you go, ask to be dropped in the "Family" area (less nudity - if that bothers you). We had several kids with us (age 8-14) it was NOT a problem. There were facilities there, restaurants, bars, rentals (chairs, floats, jet skis, water trampoline etc). There are other great beaches on St. Maarten (we just haven't been to them yet). You can do
DCL excursions or you can save a lot of money and do the beach on your own.
The Golden Eagle catamaran excursion is one of the best on the island (so we have been told by many people who have been on it - and they sure do look like they had a great day when the boat returns to the port)
St. Thomas also has a lot of nice beaches, or you can go over to St. Johns. We are going back to St. John's on our next cruise - will be doing the Trunk Bay snokel trip. I would also like to take the tram up the mountain on St. Thomas.
Have a great trip.
If you haven't been to St. Maarten before, just be warned that the island has been devestated by hurricanes in the past 10 years, living conditions are not what we are used to in the States, seems to be a very poor island. Not scarry, just poor. The people we came in contact with were very, very nice.