Apple has an "ask to buy" feature that can be implemented based on the age of the person on their iTunes account. If they are listed under 18 years of age on the account, they have to ask your permission to buy something, otherwise they can make purchases on your credit card. I don't think Apple has a way to setup a different credit card for each person. This is some info about the "ask to buy" feature:
https://support.apple.com/en-us/HT201089