Sounds like you have a solid plan in place for your daughters use of technology. One thing I would add is to teach them while they are young when using technology is not appropriate. I don't allow phones at the table during meals. At certain events the phone needs to shut off.
I know that there are apps that can limit the phones use. I recall reading about one that disables the phones ability to be used until they check in.
We do indeed have the no tablets or phones at the table rule. And when we are out having a meal too, although I do use the app to order the meal, so I don't have to leave them unattended at a table to do so.