Q: Family sharing! They ask for a cc or debit card!

Family sharing requires a valid payment method on the organiser's account (the organiser can't use any balance on their account), the organiser is taking responsibility for the family's purchases.

If you want to set up family sharing you will need to have on your account : Payment methods you can use in the iTunes Store, App Store, and iBooks Store - Apple Support

Payment methods for Family Sharing

If you're using Family Sharing and you're the family organizer, you can use the following payment methods:

• Credit cards
• Debit cards
• China UnionPay
• Mobile phone billing