Ill throw my 2cents out for drummond island. Its alot of logging roads and mostly easy trails with a few hairy spots and deep holes. Anything remotely hard has a bypass but we did not hit every trail. Its a cool place thats well marked with maps available. Free camping all you need is to fill out some paperwork. The only thing needed to wheel is a Michigan ohv sticker which was like 15 bucks and is good for a year. We didnt make it to the park but had plenty of fun hitting the free stuff.
Heres a link to my pics from the trip I took with jk forum.
http://s14.photobucket.com/albums/a3...%20Run%202011/