I've been fishing Georgian Bay near the mouth of the French (Georgian Bay Fishing Camp) since the late 70's. I've never fished there in the fall, but I've been told that the mouth of the French and into the French north to Dalles Rapids (only a 5-10 min boat ride from the mouth as it enters the bay) is the place to be. I would imagine that the Dalles Rapids are not crowded at all this time of year (it's a small area and can be hard to fish when there's alot of traffic). Anyway, if I was going that time of year that's where I would concentrate my efforts. Live bait rigs and jigs would probably be the ticket, as well as large Rapalas (7 inchers) and some fluttering bladebaits.
Hope this helps and good luck. One of the most beautiful and pristine areas I've ever fished. Ontario rules!