That's good for you and your child, that means you have to teach and introduce bitcoin to your child. But kids usually just want to have fun and a pedestal to learn.
There are so many simple ways to introduce somethings to a child, especially when we add colors and pictures without trying to push it too far, too soon. Run your illustrations side by side with doing same task with fiat currency and see them pick up nicely overtime.
If you want to keep bitcoin for your child but they do not want to know, you can entrust the bitcoin you keep to your relatives and give it to him to give it to your son someday.
Don't endanger the lives of your children by exposing them to such apparent danger. Instead dedicate a wallet for each child and create clues on how to access them and eventually mention it in your will. It would help if you often carry them along when funds are been deposited into the wallets and even in ways you earn your coins.