Mackinac is great, the marina is smack in the middle of everything, but you MUST have reservations. Actually the docks are high and the showers are weird, but the town makes up for it. Harbor Springs, & Petosky are both good and no need for a car. If you like a little city night life with your boating we enjoy Chicago if you can't sleep on your boat use priceline.com for a hotel. On Lake Eri you have Put In Bay(party town), no cars there also, unfortunately most boats have to raft off.
On Lake Huron, you have Pt Huron, Bayfield( quaint little town) and Grand Bend (great sandy beach and awesome sunset).
I sound like a travel agent!!!
It looks like you are new to the board, welcome. Where
do you live