In 2010, both those months had a free dining promotion (sans Thanksgiving week) as well as room-only discounts available. So, whatever works better for you should both be available...problem is, those promos are usually only released a few months in advance.
If you think you'll be eating a lot of tableside meals, book your ADRs now and then get the free dining when its released if you want that. If you don't think you'll be doing a lot of tableside, then when the room discounts are released, you can call back and apply that discount to your reservation.
September is less busy than November, but not by a lot (again, with the exception of Thanksgiving week). November's temperatures, however, are much more tolerable.
Good luck and have fun!!