Your itinerary will be ~600km long, and the driving would take no less than 8 hours. Unless you drive after dark they'd spend nearly one full daytime only for driving. Why rush so much? I recommend you limit your destinations to one or two, if they want some refreshing weekend trip.

Staying in or near Algonquin park for CAD100 means motel, or yurts at campsite if you really want lakeside. Staying at Comfort Inn at Huntsville is barely $100, and you can drive 20km into the park to get to Algonquin Outfitters to rent a kayak or canoe (at this moment you're almost half way back home from North Bay).

I usually stay at Algonquin Lakeside Inn. Though not a wood cabin, it's the full-service accomodation which is closest to the park. Tiny beach for swimming, and free kayak/canoe rental on site so that you'll make fun 2-hour paddling up the creek. Could be 2-nts minimum during summer month.