Tuttle Creek, though its a little drive, in Manhatten Ks.... theres also Ks. Rocks Park.
As for wheeling, it SUX anywhere in the KC area, thats why I moved to Denver, or one of the reasons, lol
we have sooooo many trails, all within 2 hours or less, anything from mild/senic to extream, been out here for about 6 years, and still havent even come close to hitting all the trails..
Best bet is to start hitting the bike shops, see if they know of anyone with some private land