It is a good area to visit. We vacationed there a few years ago and it was one of our most peaceful vacations we have ever had.
We went to Mackinaw Island City from Des Moines. We went up via the upper Peninsula, stayed up in Mackinaw City.
Spent a couple days on the upper Pen. There is a neat waterfall, lighthouses (there is a county park one you can go to the top of free), Lake Superior, going into Canada (with a passport) and many more.
I would suggest basing out of Mackinaw City. Then you can do the Island, see things in town, as well as use this as a base area for some day trips into either the upper Peninsula, down the Lake Michigan, or Huron Coast.
One thing we did was I rented a jet ski and went out on Lake Huron iwth each of the kids. It was a fun afternoon.
My wife loved sitting on the beach in front of the condo we rented, looking out at the bridge, island, and lake. Again, it was probably one of our most peacefull vacations.