Personally, I'm not in love with the idea that something harmful to children is totally okay for adults. If social media is that corrosive to young people, maybe we should take a look at that and make it less corrosive for everyone.

Some kind of "child lock" on the device makes more sense to me; a parent or whatever can child lock the device before handing it off, no need to collect images of the child in question and store them in some big pile at a private company.