My kid wants to be a pilot
The following information is based on US FAA regulations and training programs.
In the US, there is no age limit (minimum or maximum) you must be in order to fly at the controls of an aircraft. There are age limits specified in Title 14 of the Code of Federal Regulations Part 61. Here are some of the particulars:

14 or older to solo a ballon or glider.
16 or older to get a balloon or glider private pilot certificate.
16 or older to solo a powered aircraft.
17 or older to get a powered aircraft private pilot certificate.
18 or older to get a commercial pilot certificate.

In the meantime, you can get your child into one of several youth aviation programs like Civil Air Patrol, or the Young Eagles.