You easily burn the first year and just stay south of the bridge.
Have you been collecting the "You Haven't Lived Here Until" in the Sunday Freep? That is just a good start, but it is largely about so many local events.
Holland alone is a trip, and when not tulip time, the crowds aren't bad. Windmill Park and Museum are good stops. While you are at Holland, look up the times for the musical fountain in Grand Haven.
Between history and scenery, you have make up your mind which you are doing when. There comes the problem, do you want history or scenic?
When you get back from this trip, come back and tell us and we can point you at all kinds of neat stuff. There are miles of lake to look out over, but the best scenery is the dunes. Two parks of dunes, but the great one (Sleeping Bear) is way north of your current plan. As for museums, logging, historical, iron, automotive or aircraft and that does not include arts.
We travel, but we do at least one long trip in Michigan every year.
Matt