Mini scripts in Bitcoin will solve it. You will be able to programe your coins, for example, move to my son address IF I have not moved any SATS for X time.

Now days, you can also use Block time, but this involve blocking your funds for X period, neither you can't access your funds.

This video could be a good start: https://www.youtube.com/watch?v=W3XADagE6P8