Mike,
My son is 13 and a really good kid. He pulls his load on the farm and has a good attention span to keep up with the often repetitive work. He also knows how to drive the small tractors and aerates and mows for me.
All that said, he didn't pay much attention below the age of 11 to tasks that didn't involve him doing
something 90% of the time...working on cars can become way too slow for kids. The message we as fathers want to impart can get lost when we're reading the manual.
So, wait until the inner gearhead is nourished by oil changes, valve adjustments and routine stuff.
BTW, I'm thinking your son is a really good kid as well.
All the best, Mike.
Edit: Save the redo for when the bubbas can rally tackle it together.