Richard,
Looked at it years ago when we first got the camper. To camp in the front part by the country store, train, etc all the sites fill up 2-3 weeks BEFORE Halloween. Back by the big field where the Tradin' Days is held might be available but it's so far removed from the main part.
Like I said, though, that was years ago. Tannehill is a day trip for us now-a-days.
Ed
PS - also years ago DW was turned off by the Comfort Station cleanliness at Tannehill and since we are in a popup that is an issue for her (and therefore me). So she's in no hurry to go back....