Nice bunch of good advises can be seen here.
T Father, I would suggest to invest in a gliding course, no need to take a loan nor do risky investments, and it is a healthy weekend activity for a youngster.
The glider will teach your son the pure sensation of flying, will open the door to get curious about aviation and learning, will put him in the aviation emviroment and will make him enjoy the flying by being motivated (it's not yet a full time course)
After 2 years, he would be having a couple of 100s hours as glider pilot, fully knowledgeable about what he really wants to do and starting the PPL at 18 either as modular or integrated, will be a good age.
Also in 2 years time you will have a better vision for aiming to EASA or UKCAA, or both.
Airgus