I hunted Seeley Lake area a fews ago and saw whitetails everyday, it just depends on what quality you want. If your comeing in sept., by all means have an elk tag in your hand, you can always shoot deer at home. Around mid sept. they should be bugling their dang heads off. I pack a 357, 3" S.S. ruger and bear spray. I think their may be rules and regulations about taking bear spray on the plane so cheque ahead of time. Make sure you are equipt to deal with an elk several hundred feet down in a basin. Also temps duringthe day insept. can behot as he!! and down to freezing at night. Also, bring a fishing pole too and fish Seeley Lake along hwy 83, lot of places you can fish around there.
I would be more concerned about encountering a black bear sow with a couple cubs than a griz, but being that close to Glacier National Park, I would keep the thought still in the back of my head. Good luck.

Bobby