But I strongly prefer my solution!
Parent's proposal is better in that it would only take away general purpose computing from children rather than from everyone. A sympathetic parent can also allow it anyway, just like how a parent can legally provide a teen with alcohol in most places. As a society we generally consider that parents have a right to decide which things are appropriate for their children.
Spot on! The "technical" proposal from Google of a ZKP system is best seen as technically-disingenuous marketing meant to encourage governments to mandate the use of Google's locked down devices and user-hostile ecosystem.
The only sane way to implement this is to confine the locked-down computing blast radius to the specific devices that need child protection, rather than forcing the restrictions onto everyone.