Good luck with that. You can certainly do whatever the hell you please with it, but your personal feelings on the subject don't count for much in court.
As a parent? I bought the device, and therefore I own it, not the kid(s). I made that perfectly clear with my own kids in turn when they were growing up... this is not your phone, and not your laptop. They're mine, and I'm lending them to you so that you can prove your increased responsibility to your mother and I. Once the kid was old enough to buy his own phone (and plan!), and his own laptop (and ISP hookup), then he got some privacy from us (outside the home, otherwise, enjoy the transparent proxy on my network).
Until the kid moves out? Nope: my house, my stuff, my rules. I defy you to find a legal precedent that invalidates it.