It is very important that early in life, a child gets exposed to the right things, things that work from within because arrangements we make in the world around us can only be managed to a certain extent
As long as your wellbeing is subject to and enslaved to external situation, you being well is going to be accidental because nobody has 100% control over the outside situations.
There are simple forms of yoga that children can do after six or seven years of age. But it is very important that certain practices are not taught to them. I see in some places that children are taught padmasana.
This should not be done. When the bones are still growing and tender, sitting in postures that put a certain amount of stress on the skeletal system can make their bones bend.