I have not been here myself however my inlaws go every year to Atlantis with their kids.
They say it is fantastic for family. Here is a link to the site I think. (Warning: Auto Audio track plays)
Agreed with @Dog. My parents just took my 18 year old brother, my 13 year old sister, and my 6 year old brother there on a cruise this year and they LOVED it. They said there was TONS to do for everyone. Check it out!
@mammal that’s what I hear too, but if @robboh is in the U.S., and not Cuban, travel to Cuba is a pain in the keister, and I think technically illegal? Does someone know?
I also lived in Grand Cayman for 6 months, if you’re there in (I believe) November, you can make it for Pirates Week. There’s also tons of fun things like Stingray City. Check that out too.
It depends what you are looking for. Atlantis is fun in a big, commercial sort of way. At Maho Bay on St. John, you can stay in a tent, walk to the beach on boardwalks and go snorkeling, etc. What are your kids and you into?