okay.. so you are a straight shot 2.5hrs across the state to Nordhouse Wilderness area on Lake Michigan (just north of Ludington, south of Manistee) - one of the smaller wilderness areas in the country BUT, I HIGHLY recommend it on one of those wonderful autumn weekends in Michigan. The air is cool and crisp, but warm in the sun, the leaves are brilliant, the bugs gone, things quiet as all kids are into school and such again.
shoot me a PM if you want more info on Nordhouse, really a gem. Additionally about 2 hours north of you at the intersection of 65 and 72 is Hoist Lakes Foot Travel Area (do a google search) that is quite nice, it is near Mio Michigan. Can get about 20-35 miles in there but it is in the forest. My now wife, and then girlfriend, found Hoist Lakes for us to go to, and it is a fun place to explore.