North of Benton Harbor, off 63 take the Blue Star Highway going north. Not much traffic and you can see the lake from a lot of places. Many places to pull over and see the lake and dunes.
Don't know if the Swordfish WWII sub is still in the Muskegon harbor, it was a good tour.
SS City of Milwaukee is still in Manistee, tours will take you from the pilot house down below the car deck.
Lot of nice wineries on the Mission Peninsula north of Traverse City.
Harbor Springs is an interesting little town, visit the downtown shops. It is at the south end of the Tunnel of Trees.
Check your maps and try to stay close to the lake, less traffic and fun roads.