pocket edition app crashing on all apple devices

Our family has pocket edition for playing on ipads and iphones. For the last 2 months, our app opens and then crashes back to home screen after about 5 seconds of being opened. We have the newest IOS from apple installed on all devices and the most recent minecraft pocket edition update in all devices but still continues to crash. How can we get it to work again? 2 iphones and 2 ipads all do the same crashing after opening app.