Don,
I have been to Y/GT many times during the fall. It has been my experience that the Aspen along Oxbow Bend hit peak a few days either side of 10/1. Of course, this has many variables as you said.
You will definitely hit the elk rut, which of itself is worth the trip.
There is a book by Joseph Lang, Photographer's Guide to Yellowstone and the Tetons which will pay dividends. I'm sure that it is available at Amazon.
Check this out.http://wyofoto.com/Teton_Photo_Map.htm
Regardless, you can't miss with a fall trip to these two wonderful parks.