> They only can use it in our common areas when we are around, with no expectation of privacy.

Sorry, but this just feels completely off-putting and I can tell you myself, if I were your kid, I'd find a way to get myself a phone, connect to some nearby Wi-Fi and use it all the time when you're not looking.

Sure, regulate it time and content-wise, but mandate they have absolutely no privacy doing things and it will likely backfire.