I always thought that having some kind of "kid-safe" mode for web browsers would be a good idea; there are some people who would use that. People whose age doesn't necessarily have much to do with it. Having a standard header sent to websites to indicate it and making some rules about what they're supposed to do when they see it would be feasible enough.
It seems so painfully obvious that having a "date of birth" field in systemd is the wrong way to do things and can only go nowhere or else lead to bad things.