Bill, we are doing this year pretty much exactly what you are proposing for next year. Left home Dec 18, going back to Michigan mid-April (but maybe not if it doesn't warm up soon)
it's much warmer in S Fl than up in the panhandle, sometime ten or fifteen degrees warmer. Often in the 40s or low 50s at night, we have run an electric heater probably half the nights.
We have stayed in a couple of private parks but mostly Fl state parks. The state parks are MUCH nicer. Hard to book, though, because they are much cheaper too. Our favorites have been Oscar Scherer near Venice and Anastatia in St Augustine. Grayton Beach is excellent too but up in the panhandle where it's often chilly. We like to be close to the beach, Anastatia and Grayton are right on the ocean.
We are blogging about our travels in the Snoozy at www.wordpress.wanderingourway.com
We have learned one thing for sure - we are never spending another winter up north!