IF you want DUNES, go see the best, go see the bear, Sleeping Bear Dunes National Lakeshore. The park service runs a little campground nearby named the Platte River Campground.
Muskegon State Park is set in some very nice dunes as well.
There's also the NORDHOUSE Dunes, which are CRAZY BUSY all summer long. There's no (close) RV camping, very little parking and huge crowds. These are some of Michigan's oldest sand dunes, and this small portion of shore has never seen any form of commercial development. It's very pristine and relaxing, if you tune out the crowds.