Sharing in-app subscriptions for 'Bluey: Let's Play!' on two iPads

I have two children under my family sharing plan. I downloaded the "Bluey: Let's Play!" game on both ipads and I am paying a monthly subscription on one to unlock all games within the app. My other child also wants all games within the app unlocked but I don't know if paying two separate subscriptions for the same app is necessary. Is there a way to share the in app subscription for both ipads?

[Re-Titled by Moderator]