Children aren't generating this traffic, people have just switched to VPNs and don't show up as UK users anymore. What do you think kids do all day exactly?
Wouldn't it be just as delusional to think that those kids are not going to just go find it elsewhere? And now those "elsewheres" are going to be places that don't care about things like performer or content safety. Is that really going to help solve the alleged issues, both with the porn industry and with people watching it too much?
(To say nothing of the second order effects of something like this, like the massive privacy intrusion for adult citizens, or the theft/sharing of IDs to get around these laws)