This is a good idea, but not everyone has the opportunity to buy bitcoin with all the money set aside. For some of them, you will need to buy a lot of necessary things for the child, and in total there will not be much money left for investment.

Once my parents set aside money for me, which I could use at the age of majority, but it so happened that all these savings were stolen by the state and I did not receive anything.

You will still leave your bitcoins as a legacy to the children and will help them if necessary, pay for tuition, etc.