HELP - Need FL site over holidays

You need to CALL the FL state park your interested in and see if they have walk-up sites available. They usually do. Try Silver Springs State Park. I have personal experience here of seeing multiple vacant sites over a holiday. I inquired at the ranger station when renting a canoe and they told me these were reserved for walk-ups - mot available for online reservations. The sites are huge and you can virtually drive through this state park using Google Street view.