I live in Michigan and Yes, Mackinaw Island is wonderful to visit. NO cars are allowed except emergency vehicles. There are horse drawn carriages, plenty of fudge shops. You can bike around the island if you so desire. The breezes off Lake Michigan and the Straits of Machinaw are wonderful. We have sailed there several times and thoroughly enjoyed ourselves.
You can take the ferry across for the day or stay at one of the hotels. The GRAND HOTEL gets booked early (not in my budget) but gorgeous!!!! Quite an experience for a few days. Machinaw City is awesome also.....yu can sit on the shores of Lake Michigan and make yourself a picnic. ENJOY!