I have been looking into this myself, for November.
I am going there, but if you look at the Page town web site, there are videos of the canyon, replete with a zillion tourists.
It may not be busy in September. You may want to look intoCanyon X and Overland Canyon Tours (http://www.overlandcanyontours.com/xphoto
). Depending on some variables, there will be only a max of 8 shooters, and likely less. The guide holds himself at an expert at photographing the canyon.
I have not used them yet but I made my deposit, and they are very good with service on the front end.
I am VERY interested to hear how it goes, and if you are going anywhere else (like Zion, or Grand Canyon, etc.)
Hope this helps.