You have logged into your game on your ipad but you have not transferred it.... If I were you I would use the transfer method which will take the game off your old device then your son can start fresh.......
It is a bit confusing because when you use the new login feature it does say that it is transferring the games but it isn't actually transferring them from the other device - the games are still domiciled to the original device
[iOS & Android] New Login feature in Limited Games! Does not transfer your game https://forums.storm8.com/showthread....-Limited-Games!
Have a new device? Restore your original account here! https://forums.storm8.com/showthread....l-account-here!