While I played long ago in college a bit, I didn't start "seriously" playing Go until my son was 2 (just about to turn 3). I managed to acquire a small handful of cheaper sets during this time and I didn't mind if he played with the pieces so long as he was supervised to avoid choking and all that...
Over the last two years, my son has been watching me play and study. Often when I study or play, he'll get one of the other sets out and begin arranging pieces into patterns, shapes, or pictures. After a while, I noticed he was copying some of my moves, though I don't know if it was a conscious effort. He'd start to lay out knight's moves, long knight's moves, and eventually laying out nearly entire fuseki from some of my games.
About a year ago, he asked me if he could play go with me so I started trying to teach him about capturing. Liberties were still an abstract concept so we'd work on a 19x19 board, just laying out different variations of stones while he worked on surrounding them. He seemed to enjoy himself but his attention span was naturally short. He went back to making shapes and pictures. This has gone on for about a year.
A couple of days ago, I let him play with one of the boards and I noticed him talking about "this stone doesn't have any more space left" and "I'm going to surround that one if you play here." I asked him if he'd like to play a real game and he agreed. We started playing on a 9x9 and I gave him a 5 stone handicap. It was a trainwreck given he doesn't know anything about territory so I beat him severely (albeit on accident). I felt like a horrible father but he still says he had fun.
I decided that he might do better on a 5x5, so I printed off one of the postscript boards and we set about playing. I'll be damned if he didn't beat me outright in the first game. I thought it was a fluke, so I asked for another game and he beat me again. Honestly beat me. He requested a 9x9 game after that and it went downhill for him again.
So with my small novel out of the way, my question is this: I think my son has a serious knack for the game and he can't even read yet. He enjoys it and I'd like to foster that in him if he wishes to continue. How the hell do you teach a 4 year old the nuances of the game?
The biggest hurdle I see right now is the emotional one. I start to see him crack a little bit if I take more than a stone or two. I've mostly tried to praise his other moves and let him know what moves he made that lead to the capture. I'll often let him backpedal and take moves back after placing a stone if there's a real threat.
Anyway, any input is greatly appreciated!