I will refrain from giving advice on the topic, as my own personal biases and experiences may and will not apply to others situations, including your sons future.
But, I will say it is a very difficult industry, and flying, is only a small part of being an airline pilot. An airline pilot is not only a career, it is a lifestyle. Not always an easy one. Not always a well paying one. And not always a rewarding one. There are plenty of examples of people out there who have sacrificed so much, and got very little in return. While on the other hand there are those who were at the right place, at the right time, and couldnt be happier. No telling where who will end up. Somewhat of a lottery, draw a number.
Of course there is other type of flying then airline flying as well, for example corporate. But that is the most popular route.
It isnt like you see it in the movies, with layovers in exotic locations, huge salaries, half the month off, surrounded by beautiful flight attendants (well not for the most part, anyways).. So if he does go through with it, he has to be in it for the airplanes, and for the flying, or he will be disappointed.
But even with everything that is wrong with the industry, I would still do it again.
The flying is great, the industry sucks.