On St. Maarten, there is the Golden Eagle cat sail, snorkel, beach party. Lots of people on the DIS have done this and really love it.
Another option if you feel secure in your marriage is to go to Orient Beach (clothing optional

) Actually it is a very beautiful beach (the beach, the water the sceanry were awesome!!). We went with a couple of other families and had several kids ages 8 to 15 and were not worried about the "exposure". The taxi driver dropped us off in a more "family friendly" section of the beach. There 95% of the people were "properly" attired, several women were topless and there were just a handful of folks totally neked

Oh yea, Playboy is wasn't!!

My understanding is that there are sections of the beach where there is more nudity and others where there is less. If you go, don't do the
DCL excursion there because you can do it for 1/2 price (or less) on your own.
On St. Thomas we did the Barefoot Sail and Snorkel over to St. Johns. We stopped at Honeymoon bay (which in your case would be appropriate). The boat was beautiful, and the crew was awesome!! It's a smaller boat so you have fewer people. Regardless of what you do at St. Thomas, you must try to make it over to St. Johns - it is a slice of paradise!!