DS and I did the Atlantis submarine in St. Thomas. He is 8 now and I know he would still love it. Not girls, I know, but there were many little girls onboard as well.
We went to Coki Beach on St. Thomas and my DD10 loved it! The water is so clear and you can see so many fish come up. They sell dog biscuits for $1 that you can feed to the fish so you can really get a closeup look at them! The kids just loved it. We stopped at the beach as part of a tour that I booked through Godfrey's tours (not a Disney excursion; just booked through the internet).
I had heard a lot of great things about Godfrey on www.cruisecritic.com so we booked an island tour that included shopping, a guided tour and the beach stop. It was great; we had a customized tour because we had to get back to the ship by 3pm so it cost $25/person. However, if you go on their regular tours (which also include the shopping, tour and beach stop), it's only $20 per person. If you need any more info, please don't hesitate to ask me!
We did the butterfly farm tour on St Marten through DCL. On St Thomas, DD and I went to Coki Beach and Coral World on our own and had a great time. She was 9 at the time.
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