Georgia B's Quilts, W1044 Old Portage Trail, St. Ignace 906-643-7726. There are 2 in Sault Ste. Marie, but that's an hour's drive north. If you can get your hands on The Country Register (Michigan version -free at local quilt shops) it has a very extensive list by city. I keep it in the car and check it for any city we may be traveling through. DH is always happy to stop @ quilt shops for me.
Everyone has given good ideas of what to expect on the island. Rent a (very comfy) bike while you're there. The island is not that big and you can bike around the shore in an afternoon...with plenty of stops. ENJOY!