It will be beautiful there, no matter where you go! The Ice Fields parkway is a great route.
A couple of notes:
It IS berry season, and while the bears will be more interested in other things than you, they don't like surprises. Bears have a remarkably short season in which to regain the weight they lost last winter and gain enough to get them through the next one. Make noise, let them know you're around, and don't get into a pissing contest and you'll be fine.
Getting close to a rutting elk/moose/deer to get a closer shot is never a good idea. They have those big pointy things on their heads for one reason and one reason only (sex) and they have to fight others for the privilege. Rutting moose have been known to charge log skidders/ bulldozers and freight trains. They tend to lose with latter. Again, think first.
September in Banff, especially at elevation can be unpredictable. It can be sunny and gorgeous, but be prepared for fast weather changes and even snow. And remember that you need at least as much water when it's cold as you do when it's hot because your body uses water to metabolize fat to keep you warm.
P.S. These might help: http://travelalberta.com/ http://www.banffnationalpark.com/