If this wasn't more blatant political pandering and yet another attempt to censor the Internet by the fucking Brits, I would ask whether or not anyone is smart enough to realize that the world is a scary place. We don't let kids wander around aimlessly in real life, we have designated areas, usually our own homes, the homes of trusted friends and neighbors, schools, etc. where children are allowed to be and operate with minimal controls.
When we take children to the city, or the store, or anywhere else that Bad Things Can Happen(tm), they are closely supervised and monitored. Now, I realize that that's impossible on the Internet. So, instead of trying to get some kind of verification method, tld, or whatever not-gonna-work flavor of the week they can come up with, why not just have a ".kids" tld or something that only has approved kiddy-friendly bullshit then set up your connections so that's all the kids can get to? All the big sites could set up .kids friendly pages, so there wouldn't be a need for anyone under, say, 12, to go anywhere else. And 13+, they're practically adults anyway and can handle the unfettered internet.
It would be so much easier to set up a whitelist than any of these half-cocked identity schemes for political brownie points, but again this is all about pandering and censorship, not protecting children, so no real solution will ever be put in place as the regulators don't want their favorite bogeyman to disappear.