I teach this to Tariq from early age Alhamdulillah. I believe it is one of the most crucial things to teach our kids.
This will make them learn their relationship with God, about being a gracious receiver, being thankful with what they have, will always be satisfied with what we can give him, will be happy to observe the limits set AND to be a happy and contented person as a whole.
And my thankful conversation will always go like this..
Tariq, if you share, Allah will give you more and.... (And I paused, look into his eyes and wait)..... More! He will say with sparkly eyes.