My wife and I went to the Au Sable Inn on the south end of downtown on Labor Day weekend and loved it. Good beer selection. I had fried perch and she had pulled pork and both were fantastic. The waffle fries were damn good too.
Au Sable river is always fun, but probably a little chilly for that. River Rd is a nice drive, lots of forest service roads and two tracks to explore, plenty of camping, etc.