Definately go on one of the snorkeling cruises. It was amazing when we went, and look forward to taking our kids there, when they get a bit older. The hotel has a great acquarium too. The straw market was interesting, very crowded, and too me a bit overwhelming, but we were told we must go. Bring some anti-itch spray (benedril is great) There is a sand flea issue in the Bahamas (I don't know if there is a sun/bug lotion you can use that will stave off the little buggers, but you might want to look into that). They are similar to our mosquitos, but drove me nuts, as I am allergic to any bitting bugs. Please don't be alarmed about them if you haven't heard of them. Just be sure to brush off the sand outside as that is where they reside. You want to bring as few into your room as possible.
All in all, we had a wonderful time. Don't forget your passports! And have fun.
E.