I've been to all the Hyatt's in Florida. If your looking for easy beach access with kids Clearwater is your best bet. Beautiful family friendly beach located just across the street from the hotel (avoid during spring break). Rooms are large, most are suites. I also suggest a short trip to Fort DeSoto State Park, and Honeymoon Island... The beaches are stunning.

Hyatt Siesta Key / A Resident's Club is also highly recommended but cost double. The Siesta Key area is high-end resort area with beautiful white sand beaches.