The most important way to teach children is through your example. As much as it's not always possible for parents to teach their kids everything, kids are always influenced by how the parents act.
We had one retreatant who grew up encouraged in some negative ways, with a family which was always very angry. So this person thought it was normal to be angry. After their first retreat with us they said to me, "Steve, you know, a person really does not have to be angry!" They were about thirty years old, and it was the first time in their life that they understood that they didn't have to be angry.
One of the things that I am always happy to say about my father, is that I never heard him swear until I was 28. That was an example he gave to me.
When you are parents, or if you are taking care of kids as a teacher or an uncle or an aunt, etc., your example is going to influence that kid greatly. How many of us had teachers whom we really felt were wonderful and we followed their example. It's not always possible to end a child's desire, to teach a child you should not have this desire, that is not always possible. But to show by example that you are not caught up in desires and aversions yet happy and content, then they have something to aspire to.
As to a lot of kid's aversions and desires, a lot of times all they need is a substitute. Very classic with families where the parents want to eat healthier food, there is a lot of dried fruit in the house. Families where the parents are not interested in good food, there are a lot of cookies and candies in the house. It's very good to substitute one thing that is better than the other thing. So if you see your child getting caught up in a desire for something that might not be so good for them, can you substitute that desire with something else?
Although it wasn't with a child, there is a little story with me and one of my brothers in which substitution worked to change a person's desires. As a kid, like most American boys, I loved baseball, my brothers loved baseball. About 20 years ago, in my thirties, I was visiting one of my brothers.
I was already a meditator for 10 or so years and I had let go of desire to watch baseball, and spending money at a ballpark just watching other people play sports. I stopped that, it was fine with me, but with my brother had not stopped, that was still part of his desires.
One day when I was visiting him he said, "Steve, do you want to go to a baseball game, I've got tickets?" I said "No, thanks." "What, don't you like baseball?" and since he still loved to watch baseball he felt threatened by my lack of desire for it.
Yet I was able to say, "Well, look, why don't we go up in the mountains, want to go up for a walk?" Ah, he loves going up in the mountains! Immediately, the baseball game was dropped. We all went for a walk in the mountains the next day and had a big picnic. Change the desire into something that is more beneficial. So often this can be done with small children, as well with adults.