At this point in time, your best option is to get on the Florida DNR web site and see what's available and get reservations NOW! You should call private campgrounds too and those in NOW. And, it might already be too late.
We've made reservations for Florida (Panama City area) 2 years ago no, ahead about 8 months. We made reservations for Christmas and for a week in March (Panama City area again), and both times, we got the very last spot.
This year, we made reservations for Christmas week (2015) in January 2015. We're going to Florida Caverns, a little farther North than Panama City, but had no problem getting a spot.
What I'm saying is, you need to do your homework right now and get those reservation in NOW, if it's not too late already. You've only got 3 months. (IF) anything is still available.