I'm planning for a rather sedentary week long, four man paddle in the BW/Quetico, Sept. 12-19 this year, and although I'm expecting 30 F low for a couple of nights, it could easily drop to the mid-twenties.
Like you, I'll sleep in a tent. I'm taking a BPL 180 quilt, and a Stephenson DAM. For the dropping chilly temps. of late aft. and early evening camp slacking, I have a pair of BPL insulated pants and a Montbell Alpine down vest, which I can also wear sleeping. I've slept comfortably at thirty F with this kit in the past.
I understand that your hiking/camp style could place more emphasis on a warmer bag, less insulating clothing, and less weight.
Have a great trip!