I desperatly wish my parents taught me GTD as a child, haha. I'm sure I'd not have been to enthusiastic about it as a youngin', but man, my early projects would have been so much more inmpactful and it'd have given me a great self-confidence boost to get those projects done at a young age.
Something even better: Teach kids by example how to acquire habits.
It is the best skill you can teach a child, as she will use it the rest of her life. And kids learn much faster and with way less effort than adults.