I agree with Tripalot, that'll be a lot of driving - particularly that stretch from 6 mile to MacGregor. And, to be honest, 6 mile never impressed me much.
I'd suggest making Algonquin a 3 night stay, skipping 6 mile and going to Awenda for the nights of the 13th/14th and then heading back to Toronto.
As far as where to stay in Algonquin (and looking at availability), Two Rivers campground has open, smaller sites and is close to the camp store (and closer to the dump station) while Canisbay has large secluded sites but is farther away from everything.
