Is banning e2e encryption really going to keep your niece & nephew safe? All the surveillance in the world cannot and will not replace involved parents & family, and will likely just create many more paths for your niece & nephew to be harmed now and in the future.
I have a niece & nephew I love dearly, too, but we rely on knowing where they are, what they're doing, who they're interacting with, and most of all, raising them as *thinking* humans who know what is and is not appropriate for anyone (family included) to ask of them and do to them rather than hoping the government will do the parenting/extended family job for us.
The research and empirical data of prevention of sexual abuse is clear: if you're relying on surveillance, you failed years before elsewhere.