Hello,
I have a question, what does your son wants ?
Is becomming an airliner pilot a dream of him ? Is he sure ? Absolutely sure ?
I wouldn't wan't to be an airline pilot for all the money in the world, i find it a very hard life, problems to have a normal family life, and at the end of your career, all you can do is flying, nothing much more.
For money and job security there are tons of better things, believe me.
BUT, if all he can talk about is flying and he really really really wants this, go let him get his PPL, you can start with the theoretical exam, it won't cost you that much on books or maybe saterday school lessons that starts in september and if he get goods grades and enjoys it to the fulliest you can move on to the practical part.
Good luck and all the best!