I know kids steal or fake ids but yeah not a reason imo to not card people hah

This whole post exists because the need to card people and then use that card to verify that person and how it opens up the door for your identifiable information getting stolen.

The child would need to get the app and have it verified (id and face scan, bank logins).

How would that work, be around to verify with the app or something?

The way your proposed solution works is that the verification process is asynchronous. The government verifies the identity in the app and then the app is used to verify identity elsewhere. Those are two separate steps that don't happen in succession. There's bound to be some time between the two steps if for no other reason than for the government to push the new key into third party databases (because if it uses the pull method then you've reintroduced government tracking. That means there's a timeframe where person A verifies themselves, gives the key to person B and then person B uses the key until it expires. Now you need to start building in safeguards to prevent keys from leaking from within the app.

I'll ask a counter-question since my point was is it really preferable to parents parenting. How complex (which increases how costly the development will be) and how inconvenient does it have to get for you to consider that perhaps parenting is a better solution? Because I'll also add this, this solution doesn't prevent "bad parenting" because a bad parent can just identify themselves and let children use their identification to bypass whatever the kids want to bypass.