Are you going on a cruise ?, if so the cruise line has activites that you might be interested in. You can also do them yourself with a bit of leg work, and save a few bucks from the cruise prices.
The diving in all of thses islands is spectactular,Aruba and Barbados especially because they are farther south and the water is even warmer.
Lots of things to do and see, do some internet investigating and you'll come up with more things to do and discover than time.
Regards and have fun