It's about 360 miles from Fort Wayne to the Lower Peninsula, so probably about six hours in the car for you. You'll need to take one of the passenger ferries from either Mackinac City or St. Ignace across the Mackinac Bridge (toll required) to get to Mackinac Island. There are no cars allowed on Mackinac Island, so you will need to park your car at one of the ferry terminals. More information about ferry services to the island here: http://www.mackinacisland.org/transportation/