I agree with your assessment as well I've driven Shannonville and it's a great track with good runoff areas for those times that you have pushed the car beyond your limits. I've never driven Mosport but have gone on a ride along and it's scary at times with the walls being so close to the track. The other option is Cayuga raceway they are known for there dragstrip but did build a 3km race track back in 2001 I haven't had the chance of going around it yet but from the picts that I've seen it's a good track with some challenging corners.I used to spend a lot of time on the tracks with my GSR and CRX.
Shannonville is the way to go..
Check out the local clubs and even try to rent an hour or two of open track, they have special rates in the evenings just before sunset.
Mosports Park also has a race track, this one is more for the advance drivers, as the tracks are quite hilly, if you don't have the skills, please don't attemp..
Cayuga road course track