Google, here, are taking the right approach. Wall off bits of the internet, make _them_ safe for children, and then white-list sites into it.
By creating child-friendly versions of YouTube, etc. they're creating a safe space, and not encroaching on anyone else's rights to make videos that aren't suitable for kids.
I don't really understand why this hasn't caught on much before.
Original post on Dreamwidth - there are comments there.