The good news is that Florida is surrounded by sand, now you need to decide on the type of beach you want.
Consider age group of your crew and what you think is relaxing.
Cocoa Beach - Atlantic Ocean, bigger waves, brown beaches, can watch the sunrise
Clearwater (soft white sand) & St. Petersburg beaches - Nice beaches, offer changing areas, smaller waves, white sand, and can watch the sunset!
I like Clearwater and the water visabilty is normally very good, so with goggles kids can see in the water.