I agree with Steph on Key West. It is just not kid friendly, unless you do one of the time shares, and even then, you are not talking beach.

Clearwater is good, and although I have not been to Coconut Point, everyone raves about it...even the employees at Key West and Clearwater!

If it does not have to be Florida, then my recommendation would be Gainey Ranch in Scottsdale. Multiple pools, little kid beach, gondola rides, etc.