I'm going on the Freedom the week before you but the Western Carib. cruise. I've been to all of the ports that you're going to the week of the 22nd and unfortunately I don't think any of the ports have 4 wheeling. CooCoo Cay is RCCL's private island so the activities there will be very limited. St. Maarten has segway tours (I think) but when I went to St. Maarten my wife and I decided to go and have fun on the Nude Beach.
In St. Thomas we didn't do much, we took a tour to Black Beards Castle and also went to Megan's Bay.