Congratulations on your son's acceptance!

If his interest in computer science / computer engineering is very clear, I strongly recommend going to a direct program in computer engineering. Unless there is something very specific he wants out of EngSci, you can get mostly the same thing through a Core 8 program (even machine learning and robotics stuff).

It's very easy to switch from EngSci to Core 8 (just drop by the admissions office before the first day of classes).