I wonder if it would be any colder than a summer evening camping in the redwoods here in California. It's warm during the day, but cold enough at night and early morning to wear pants and jackets and warm your hands over the campfire. If that's how a December in Florida is, then I think we can handle camping at WDW in December. However, if it is much colder than that (being that it is winter in Florida), I would not.
On second thought, maybe hauling all that camping equipment in the plane is not a good idea, so we should probably just stick to a hotel, even though it costs more.