Looks like a cool trip. I've been to many of the places you are going to traverse and by the looks of your route. I think one of the coolest things you are going to see is the Mackinac Bridge.
I rode across it (N to S) in 2011. You can look through the grates to the water about 200 feet below... It's a strange experience as your bike will wander on the grates. The right lane is paved, the middle lane is steel grates. If you have any queasy feelings the paved lane can be your friend LOL.
As for Mount Rushmore, it used to be cooler than it is today. In the past, the road went right up to the base of the mountain. Unfortunately, that road no longer exists. It has since been re-routed and in its place they have built a Welcome Center and commercialized the area. Regardless, its still a cool destination, just not as virgin as in the past. I don't think you could get the attached shot today... There's a building in the way.
Have Fun!
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