Hey Mike!
There are a lot of very nice dunes on the eastern shore of Lake Michigan (the Michigan side). Here in Wisconsin, there are not many dunes on the lake, but there are some nice barns & the cool sandstone formations of the Dells along the western part of the state.
There are many waterfalls here & in the upper peninsula of Michigan (kind of like Washington without the mountains & ocean)!
I'll bet if you check out various state's websites, you'll find some great stuff to plan your journey!