please be careful
Mackinaw Island is absolutely my favorite place to fly into. It is only two hours away in my Cessna. I spent many summers on the island in my youth and still have family living on the island.
If you are only visiting for the day let me recommend lunch at the Grand Hotel golf course or at the Porch at the fort. They are both an outdoor cafe and the food is reasonable (?) but with a great view! Many other places but if I only had one day, the golf course would be my lunch spot.
Be prepared to walk a lot! It's the best way to get around. The two horsepower taxis are cheep but also slow. Bikes allow you to cover a lot of area in a hurry but please be careful as more folks that the authorities care to talk about get banged up or even die in bike accidents.
If it is warm and sunny, feel free to grab a lounge chair at the Point resort and take in an incredible vista.
Can't say enough about the place!
One word of caution! You will have to fly over Lake Huron and/or Lake Michigan to get to and from the island and on to Kosh. The water temps are in the hight 30's or low 40's this time of year. From the mainland of Lower Michigan to the Island is about 8 miles of open water with NO options. The island itself has only one option, the airport. There are no beaches, roads, or fields to set down into in an emergency. Take flotation and go in high.
Wish I could join you. I do plan to fly to Kosh later in the week for a night or two in the back 40. Hope to see all of you there.