Jacksonville, FL...Hannah Park right outside the gate to Mayport Navy Base. Nice park with lots of trees and within a couple miles of downtown Jax Bch. Sebastian Inlet in Sebastian, FL...off A1A just north of Vero Beach...its right on the water. St Augustine is always nice, so is Jetty Park in Cape Canaveral...you can watch the cruise ships come and go, fish, and eat at some great local eateries like Grills at the Port.
I second Rock Crusher Canyon...great place. And Destin.
If you're in the area of Orlando, reserve a few nights at Ft Wilderness...its great even if you chose not to do the parks. You can hop on the monorail and hop to all the hotels...great during the holidays.
Enjoy the search.