Of your approach in your children’s lives.
Yes, it’s important to restrict access to unlimited smartphone time and content. But, when you put such harsh measures in place, your children will be the brunt of some very cruel jokes and will be an outcast in many situations. That’s your right, but there will be real social anxiety created for your children with such a militaristic approach. If you hold to this strict policy, your children will resent you and they will suffer later in life with tech addictions.
Let me suggest an alternative… it does require purchasing double the hardware, but you give a restricted device to your child, then you create a clone of that device that you have full access to. Every email account, every app, you’ve got full visibility.
I was much more lenient giving my kids devices because I had a full copy of what they had with them. Sometimes they’d try to be tricky and delete a message or a photo, but they’d always mess up before the cloned copy existed that I could see.