The better route would be through Sarnia, which would be about 4 hours.
Chicago is approx. 523 miles / 836 km from Toronto. MapQuest.com shows the drive to be just over 9 hours, (crossing at Pt Huron / Sarnia) but that is non-stop driving. You will need to factor in additional time for breaks, meals, traffic delays and clearing through Canada Customs at the border.
Presuming that you will be driving a rental car, ensure that the car rental company notes on the rental agreement that they authorize you to take the car into Canada. You may be asked by Customs when entering Canada, or when re-entering the US, for this documentation.
Route through Sarnia would be a better option although I think even 8 hour drive is manageable.
I would wait until you cross the border...can't recall the name-might be the Holiday Inn-but right by the Blue Water Bridge was a brand new hotel being built last winter (or was in Fall-believe Fall) Its more than likely done and open now..I would look in to that..It be perfect..you get past customs and it is like a 3-5 min drive away..maybe 2 mins.
Toronto would be 4 hours max after ward..that is with stops.
You need to look at maps..you could take the 401 in to Toronto or the QWE to the Gardiner..which would take you right in to the downtown area..it depends on where your hotel is at.
You can make good time in Michigan..speed limits 70 mph so you can go a bit faster..stay away from Detroit..either head North on I-94 to I-96 to I-69 or head East on I-94 and go right to I-69..talk to AAA if your a member since they would know were about the road work projects are.
Having done this drive a number of times I would suggest you drive Chicago to Windsor the first day, stay overnight in Windsor, then drive on to Toronto the next day. It's a nice 4 hour drive on both days on 4+ lane freeways.
Windsor has many hotels, including all the North American brand names, and since you will have some time in Windsor I would suggest a visit to our sculpture garden along the Detroit River while you are here.
Well Windsor would have more places to visit..places to eat..the Casino...hotwire could get you a good price on a room. If you go that way be sure to fill the gas tank up..off the 401 the rest-fuel areas are being rebuilt last I seen in the winter and they had a long ways to go..just flat land last I seen..I had to leave the 401 and go 5 miles away to some little bitty gas station for fuel--then had to go 5 miles back to the freeway. At least there was signs from 401-that was nice..so much farm land and nothing else around..
Either way fill up right before crossing the border since gas is about $1 a gallon cheaper in Michigan.
Good a good deal at the Staybridge Suites of 102 CAD per night.
Thanks for all your helpful advice, much appreciated.
According to GOOGLE MAPS, the shortest route from Chicago to London is I-94 to the I-69, crossing at Sarnia, Ontario... a distance of 658 Kms and an Estimated Driving Time of 6-1/2 Hours... not accounting for Traffic, Construction, Weather, Breaks, or the Border Crossing.
Distance from London to Toronto is 196 Kms (2:10 Hours... again under "ideal" conditions).