Great that you have your 2nd iPad!
Yes you can play on your 2nd iPad until the team releases game updates for Farm Story 2 and Fantasy Forest.
Once the game updates are out,
1. Start both game apps on your iOS 12 iPad to make sure you can get into the games
2. Close out Farm 2 app
3. Use the Login feature in Fantasy Forest to move all your games back to your iOS 12 iPad
Once this transfer is done, all games under your Storm8 account, including Fantasy, Farm 2, will be transferred over.
P.S. Don't worry you wont lose anything during the transfer. You just need to make sure you remember your S8 ID and password and also properly save your game progress and close out the apps before you start the transfer.