Quick question about playing simultaneously on 1 game

So, I brough a Switch 2 and the kids want to play Minecraft at the same time on a Realm server. Not an issue in theory, but it seems that I can't have multiple digital card of the same game, which is odd. Do I have to buy a physical card to play Minecraft at the same time or is there a way to buy multiple digital copies ?

Do I need to have a different setup, maybe in the family account or setup users or devices differently ?

Currently my setup is switch 2 is the main device and associated with the switch 1. Everything is under the family account. Not sure if more information would be required.