We boat at the Southern end of Georgian Bay. It took us a few years to get all the way to the North Channel. I'm glad we did it, and we'll return every year! It is that spectacular.
Thomas Bay, which is on the Georgian Bay side of Killarney is a great spot for a night or two, Covered Portage Cove, on the other side of Killarney is a fun spot also.
For provisions, I'd skip The Sportsman and go to Little Current. The Sportsman is fun for an evening though.
There are so many spots you can go to. Shawanaga, on the Georgian Bay side, is a great spot to stop on your way. The Bustard Islands can also be fun.
My favourite was the Benjamins. Such a great spot, lots to explore, nice water, and we met lots of great new friends.
We're at Bayport, in Midland. If you end up at this end, send me a note.