Ditto to the foregoing advice. I camp in Michigan through the end of October. Some the weather gets pretty cold. I really don't use the ceramic heater but it sure wouldn't hurt. Ventilation is important ... to let condensation out and to keep the heat moving.
I wouldn't worry too much if the temps get in the 20s. I've woken up many times to a frozen water hose to the city water connection. Normally thaws by mid morning with no damage to the plumbing system. Call me lazy
Enjoy the beautiful fall weather, empty campgrounds and peace and quiet. My favorite time of year to camp.