In Barbados, Accra / Rockley Beach and Bottom Bay are both popular destinations although there are many many beaches. If you're looking for more than the beach options my sister and her grown children did a Snuba tour there with RCCL and said it was a blast.
In St. Thomas Megans Bay is by far the most popular although I wasn't as impressed with it as some here have been. Shopping is the other main attraction there, at least it is for my wife and any of the ladies who like jewelry.
St. Lucia was among the most beautiful islands I've ever visited. Much like Jamaica, which is also a beautiful island the people there are very aggressive. To the point of making travelers uncomfortable. If you do venture out the volcano is pretty cool. You can get up close to the sulpher oozing and bubbling out. It stinks but is fascinating. Don't bother with the falls, it's a trickle. Also rain forest options that are great. Didn't do beaches there so can't help with that. If they'll allow you to ask for a cab drive by name ask for Linus cab #TX911. He's great, personable, knowledgable and I kept his name and cab # in case I go back. I'd track him down if you can. You can negotiate the rates at the Tourist info center if you're not doing a planned excursion through the ship. The negotiation is not a fun process but worth it.
I'll cut this off and let others comment on St. Kitts and Tortola. Never been to St. Kitts and it's been a long time since Tortola.