If you've been shopping around for parental controls to help manage your kids' Apple devices, you might want to put on the brakes: The new operating system, iOS 12, has a feature called Screen Time that might have what you're looking for, and it became available on Sept 12. As with any parental controls, they're best used along with guidance and ongoing conversations to help your kids learn to manage their own media use. 

Screen Time lets you see exactly how much time your kids spend on their phones and tablets, the times of day they're most active, and which apps they use the most. You can also set app time limits, filter inappropriate content, and schedule "downtime" – basically, shut down the device – whenever you want. (By the way, you can do this for yourself if you need help managing your own device use.)