I recommend that you install android keylogger
https://www.hoverwatch.com/free-android-keylogger on your children's phone. It's a simple program and it will run discreetly on your child's phone. With Hoverwatch, you can retrieve timestamps of deleted call logs and messages. Furthermore, this spy app takes things a notch further by giving you a real-time location of the target’s device, all thanks to the GPS tracking feature.