Here is how it should work, MS take notes. (at least best for me)
First a settings page, what I want Kidzone to access. Certain games, media, apps, incoming calls, incomming texts, make calls, take pictures,(anything else feel free to add).
The main point is that to turn this on, it is through the Lock Screen. One passcode unlocks your device, how we are all used to, one pascode activates Kidzone.
This works great for me as I get pestered for my phone when it is in my pocket and also if the kid sees a code, it is one that restricts their use, or I could give them that code right off that bat.