Hello William,
It was 11 years ago my parents were faced with the same question.
I'm glad they said yes.
Like your son I was bought a lesson for my 14 b'day. I had always wanted to fly. I loved everything about it. From that moment on i was hooked.
When my parents said yes, they made me go out and earn some money, as they did'nt want to hand me the money but anything I earned they would match (usually with a bit more).
I think getting the ppl is invaluable. I lets your son decide whether it is a great hobby or is it something he wants do for the rest of his life.
I got my ppl at 17, sold my soul to the devil and went to oxford and did the f/atpl full course.
Got and lost a job while training due to sep 11. Started instructing, got a job with a loco, and am now in the right seat of a 777.
My advice is to encourage his him if you can afford it, and maybe get him to do a few jobs (teach the value of money and all that). When he has to work and save every penny to go flying it will put everything in context.
On the job front, as everything its very cyclical (think thats spelt correctly). At the moment their are a lot of jobs out their. A lot of my friends have got jobs with minimal experience (turboprop and jets)
Hope this helps
Seabiscuit