Why is Funamo turning itself off?
It is hard to tell based on the limited information. First thing you can try is keep the phone with you for a couple of days and see if it happens too. If it does not happen to you, it means that you kid may have found a way to kill Funamo. Then please check if Settings is protected, Device admin and protect device admin are enabled.
If it also happens to you, try to see if you can find certain pattern when it happens. For example, dose it happen when you restart the device, or when you enable power saving mode, etc.