Hello OwenW100,
We understand that you want to know if you use an iTunes gift card for an in app purchase will the family member still get a purchase receipt. We're happy to provide some information about using gift cards with Family Sharing.
If a family member has store credit on their Apple ID then the credit is used before any remainder is charged to the organizer's payment method. The family organizer will still get a purchase receipt for the purchase. The iTunes Gift card must be redeemed onto the Family Member's account and not the Family Organizer's account.
You can read more about Family Sharing purchases and payments here:
Family purchases and payments
Let us know if you have any questions.
Thank you for using Apple Support Communities.
Take care!