We should teach them at the second stage because at that stage they can buy chocolates snacks and even rum errands, to make them understand that there is a digital currency known as bitcoin,this will help them know quick about bitcoin in other to join the moving train when it is the right time for them. I heard a boy of 15 that his father has 7 btc and the boy was the next of kin to these bitcoin. Lack of proper knowledge on btc made him gave out one btc to someone.
Losing 1BTC may teach the kid many things such as trust. While the article suggests 7-14 years old is the right time to teach a child about investment, I would first establish his skills to live without having the help of someone like teaching him to catch fish with a fishing rod or find a job even in Mcdonalds.
Let him start from the lowest and start climbing up and then let him join me to start a business together and then accept BTC payment. This is my plan when my kid is at the right age already. Maybe after this, he will learn reading charts and trade b better than me.