Good friends just returned fron the Constellation, and these were their experiences. They did the Joll Rodger cruise in Barbados and had a good time but would not recommend it with kids they have a six year old. I think we are good with the catamaran sail. They also did snorkeling trips in Grenada and Antigua through the cruise line. They said the one in Antigua was great. The boat in Grenada was a little run down. Also, in St Thomas they went on their own to Magens Bay and then shopping and they felt the taxi rides were quite expensive and that they probably should have booked a similar trip through the ship. They do offer a beach and shopping trip. I am pretty sure that we will go it on our own to Magens Bay, I am not interested in shopping. We have been to St Thomas quite a few times. I am shopped out!! We have necer been to Magens bay and are still debating there or Coki Beach. Hope this helps.
We were on the same cruise a few weeks ago - only excursion we booked was in Barbados we booked Silver Moon on our own - a catamaran that takes 12 people - makes 2 snorkeling stops and serves an excellent lunch - the crew was great and really enjoyed the day. In Antigua we found a friendly cab driver who took us to a few spots (Nelson's Dockyard, Shirley Heights), to the beach for a few hours, picked us up to go back to the ship. On Grenada we just took a water taxi to Grand Anse beach, and on St Thomas we took a cab to Sapphire beach. Overall we had a great trip.
Enjoy your trip!