My kids are 7 and 9 now and we still love playing martial arts games. Even when they were so little that they had no understanding of what the movements meant, I played lots of tag and tickle type games (e.g. "smell my feet", "Nagasaki nose throw") with them. They learnt the footwork implicitly before they ever started training in a gym. But more importantly, they love it and I love it. We built on those games over the years but they are still playful. One of the kids will throw a random kick at me, we call this "ninjaing", and the game is on. I think it is these fun times that will stick in their heads as they get older and I hope that they reproduce those playful games with their own kids. I bet your youngling will keep coming back to you for more if you make it a game, especially a game they can win.