Q: Can a iTunes card be used to pay for purchases with a family share?

Hello there, clavere.

The following Knowledge Base article offers up an answer to your question:

Family purchases and payments

http://support.apple.com/kb/ht201079

Making purchases

After you set up your family, any time a family member initiates a new purchase it will be billed directly to your account unless that family member has gift or store credit. First, their store credit will be used to pay the partial or total bill. The remainder will bill to the family organizer. As the family organizer, any receipts generated by the transaction will be sent to you. Learn more about how iTunes Store purchases are billed.

Thanks for reaching out to Apple Support Communities.

Cheers,

Pedro.