Tim,

I think for a first trip I'd just go from Beaverhouse to Sue Falls via Quetico and Cirrus rather than try to make it a loop.  Again, this will allow plenty of unstructured time for the kids.

I'd also do it in that direction for two reasons.  First, you'll be hitting the heavy portaging at the END of the trip instead of at the start.  If you hit it at the start the kids might decide they hate canoe-camping because it's "too much work" before the trip really gets going.  Second, the prevailing wind should be from the west and thus theoretically at your backs instead of in your face as you travel.  We all know that an actual tailwind is a fantasy but a guy can dream, right?

I'd go via Cirrus instead of Kasakakwog just to avoid the Kasakokwog to Cirrus portage.  Haven't done it myself, but have heard it's not an easy one.