cant buy Xbox Game Pass for PC

Also to add - I have baught minecraft on the Microsoft store, but I cant buy the game pass on the pc xbox store

If i understand the problem, you want to buy them both an Xbox Game Pass subscription to play on their respective PC's ? Buy an Xbox Game Pass PC sub for each or a Ultimate Game Pass. Log their account on Xbox beta app on PC and buy them the correct sub.
Or use xbox.com with their account correctly sign in and buy them Xbox Game Pass for PC.

I dont think Minecraft is in Ultimate Game Pass or Play Anywhere on PC.... i just had a look on the Xbox (Beta) app on PC and i cant find it.... but you can get it from the Microsoft store on PC and buy it...

Hello, how are you? My name is Mateus. I'm an Independent Advisor and I'll be glad to help you today.

First, welcome to the Xbox community. It is necessary to link a conventional payment method to your accounts, such as a credit card, debit, or PayPal if it is available for your region, when adding the payment method, rest assured the amount will be charged from your Microsoft store digital balance if choose it later.

*Thank you in advance for contacting, I hope this can help you.

Hey,

I'm unsure if that offer is still on-going since if I'm right it was E3 related, if it is you'll need the funds for next month aswell in your account, however it won't be taken from your account if you disable recurring billing after purchasing your subscription.