I know what his game is and I try to work with what he has just like someone else would work with what I have. That's the way instruction should be. My goal with my children was to get them to like the game of golf and play it if they wanted to. My feeling is a kid is ready if he's old enough to play three holes without chasing a frog. What I mean by that is playing three holes takes about 45 minutes to an hour and they need to be able to keep that long of an attention span.
Some kids can do that at age four or five.
Others may be 15. You're wasting your time and effort if a kid wants to be a kid and not do anything else. Let them be a kid. People enjoy a playable and pretty golf course. I shape some of my designs as the result of a story I relate that describes what the average golfer and a pro look for in a golf course.