I never had children, but if I had a kid, when he or she turned 15, I planned to give 'em a nice motorcycle.. -in seven or so cardboard boxes of parts. And a shop manual and basic set of tools.
I got darn near everything that same way when I was a kid. I started mowing the neighbor's yards, then one day I noticed this old BSA in the back of a guy's garage.. He had taken the engine apart and couldn't figure out where to go from there ..Que the big little kid smile I noticed that approximately every 10th house had a basket case motorcycle, sooooo...
Soon, my folk's backyard had a dozen different bikes.. Vespas, BSAs, Triumph, Hodakas, and a bunch of Japanese stuff. I became a half-fast bike wrench in a few years from that.
Bugs are just as easy to teach a young'un how a machine works. If you build/fix it yourself, you're gonna appreciate it more, as well as catch the Gearhead Flu we all have on this site.
Build it, ride it, love it 'till I die. -Put that on my tombstone, amigos.