I know 3 airline pilots.
1 captain and 2 First Officers.
They all have shares in light aircraft (as do I), there’s a reason commercial pilots also fly other aircraft.
I was talking to a commercial Captain the other day who is saving up for an RV.
OP, the question to ask is whether your son wants to fly or whether he wants to be an airline pilot. They’re not necessarily quite the same thing.
I love procedures and RT, I’d quite enjoy being an airline pilot. I also enjoy swooping around though, so, I have a well paid job in IT and I do both in light aircraft.