I figure I'll bring my duffle bag but it won't be full, so it ought to be easy to crunch it in wherever - much better than one of my hard-walled suitcases, anyway, which WOULD hog space.
Aside from that I'll have my laptop in a small computer backpack. I can leave some stuff (like my headset) at your house while we're in Ontario because I'll really only be using it on the plane. That'll make the laptop bag take up less volume too.
I don't think we're going to be pressed for space, unless everyone decides to bring a suitcase and two bags!