I would generally agree with clunckdriver. The Seneca grads that I have been exposed to are of lesser skill and knowledge than those from other universities around.
With that said, Seneca did have a program where the top students would be hired by one of the Air Canada Express carriers (Georgian, Jazz, etc.) so it is possible that the pilots clunk and I have been exposed are those who "passed" rather than those who excelled.
The universities you've mentioned are all Ontario based and with Fort Frances listed in your location, I understand why. However, there are other programs out there where the caliber of graduate is much higher. For example, I've found the majority of graduates from Mount Royal in Calgary (MRU) is much higher than other schools, but on par with those from Western. Therefore, widen the net.
Your son is in a good place right now for as far as job prospects go, but then so was I at your son's age in 1999. Things were progressing decently until a crisp, fall morning in 2001 and then the show suddenly stopped. Off-Broadway cancellations have more notice, and the same thing can happen right now. Hiring is booming right now and if he completed his ATPL today, he would have a job with Jazz or Encore tomorrow. But that can all stop in a heartbeat and he can end up facing 7 years without a job in his chosen industry.
At the end of the day though, your son will graduate with around 200 hours total time, a Commercial Pilot License, and a Group 1 IFR. Just like every other student. So his job prospects and success in the industry will ultimately be more about his personality and professionalism rather than the school that is displayed upon his resume.