I do the ride to Canada almost every year.
Instead of doing 401 to T.O. - head up to Sarnia and try the 402, that comes down and connects to the 401 outside London (BBQ at Chrome's - he offered

)
Iwould then head north on any fair sized road and the head east on any fair sized road. Ontario has a mostly grid style roads - especially out in the country side - It can take WAYYY longer, but can be really nice.
Otherwise I would take the 403 to T.O. and then go 427 to 401 to 400 to Barrier. (And remeber once you are on 400 you are also on Hwy 11 - Yonge St - the world's longest continous street).
If you are going to Montreal - I would go from Barrie around Lake Simcoe catch up to Hwy 7 -- meander over to 416 and then to the 401 .
Normally I take 401 to 40 then get off on Hwy 132 and ride the south shore of the St. Lawrence river , then come back across either at the Champlain or Victoria bridges (the Mercier bridge brings you through too much traffic for me).
Be warned though - once you hit the Quebec roads system, the roads can be pretty crappy highways too!
I will be (hopefully) doing a ride up there in June for a nephew's wedding in London and will probably go visit other family in Ottawa & Montreal as well. After all - London is only 900 miles from here --- and Montreal is only 1200 miles from here
But enjoy the ride & get some poutine!!!!