Bandit,
I had no interest in aviation either at the age of five (but by the age of about ten I did), so things might change. I was more interested at the time in taking Granny's television to bits and then putting it back together again...
Thinking about it, I didn't end up doing much that my parents were interested in - your lad will find his own thing to entertain himself, so it will be fun for you to discover what he does!
T.