Great, it reminds me of when I was a kid and played at "space". I used to get a load of old war surplus radios, lots of dials and switches and make consoles. Of course nothing actually worked, this is so much better. Lucky lad.
He's 9, so I figure I have 3 or 4 more years MAX where he will hang out with me and work on stuff
Yes but when he comes "out the other side" it can happen again. 
One of my favourite quotes normally attributed to Mark Twain:-
"When I was a boy of 14, my father was so ignorant I could hardly stand to have the old man around. But when I got to be 21, I was astonished at how much the old man had learned in seven years."