We went to Disneys Vero Beach last may and LOVED IT. The resort is beautiful, lots of family friendly activities if you want to participate and cool kids areas, plus the beach and a large pool with plenty of room. We had 2 bedrooms, living room, full kitchen, and balcony. That would be fun! DH went deep sea fishing one day and had a blast as well, and they have a massage therapist, putt putt, movie rentals, etc.
I want to drive to the Keys next time we go, myself, but I've never been so I can't recommend it necessarily =) Miami would be fun to visit one time, too.
Good luck planning your trip!