I also recommend Celine Too. They often pick up cruise ship passengers for one of their sails. There are lots of opportunities for snorkeling and swimming which the kids would probably love. The food is amazing! You can contact Neil directly OR contact Dave who also sails with him. Dave and his wife have a booth just off the cruise ship pier and they specialize in day trips for tourists (incl. booking trips with Neil) We did a dune buggy tour of the island with our group of 11 and everyone had fun! Our group also loved the Celine Too and we ended up having the whole boat to ourselves which was very nice! http://www.happyhoursxm.com/