St. Maarten:
*there's Great Bay which is where the Magic parks. It big and the water is calm (read boring). Advantage: $5 per adult for all day water taxi pass from the town to the Magic. Shopping is right there. Water toys there too (jet ski, water trampoline, etc)
*Orient Beach: a beautiful beach in a beautiful location on the French side. 15-20 minute taxi ride $8/person each way depending upon quantity of passenger. Clothing optional - facing the water the farther to the right you go the less clothing you will see

The water has waves here so its more fun to play in. There are jet skis, trampoline, wind surfing, para sailing here along with facilities (restrooms/food). Easy to do on your own and much cheeper than
DCL's excursion to the same location.
*Golden Eagle Catamara excursion: Sailing, Snorkeling and Beach party. Everyone has fun on the trip.
*12 Metre Regatta excursion sounds fun
*Dutch side you can gamble on the French side you can let it all hang out on the beach (clothing optional)
St. Thomas
I've only gone over to St. John and it's spetacular. Pick a snorkel excursion and you really can't go wrong!!