The children is a smoke screen. The government wants control. Encryption threatens that control, because now citizen communications can not be snooped onto, so nobody knows what those sneaky bastards are up to. The government hates being in that position. So they invent plausibly sounding excuse (which is usually protecting children, because it's politically impossible to be against protecting children unless you're a crazy libertarian and nobody listens to crazy libertarians) to change this. It didn't take long for surveillance which was sold under the guise of fighting terrorism to be abused for every government purpose they liked, from drug war to getting dirt on political opponents. Same will happen immediately with this law, if it gets passed.