I would really recommend visiting Waterloo if your son is interested math or engineering and you’re going to be in the area. The campus and culture is very different from that of U of T. Waterloo is a very math and engineering focused school. It has humanities etc but they are a very minor part of the school. It’s also unique because of its co-op program. As a result, Waterloo prepares students to find jobs after graduation whereas U of T prepares students for grad school. Visiting Waterloo only adds one hour to the drive between Toronto and Rochester.
D16 is at Waterloo in math and S14 is at U of T.