IOS - You can play on two devices as long as you are logged in with the same App Store ID. Please make sure you are logged into 'gamecenter' as well. However, you cannot play on two devices at the same time.
Android- At this time it is not possible to play on 2 devices on Android devices. Our team is looking into this issue however, we are unsure on when it will be available. We apologize for the inconvenience.