You can use your Android subscription on any other Android device you own, as long as the main Google account on each the device is the same. To change your current main account, please do the following:
- Delete PlayKids;
- Sign out of your Google accounts. To do this, click on "Settings" on your device > scroll down to Accounts > Google > tap the account > Remove account;
- Enter Google Play Store and login with the account with which you already have a subscription.
- Download PlayKids again.
If you want instructions on how to change the email address registered on your Android device, click: https://support.google.com/googleplay/android-developer/answer/139626?hl