Transfering iTunes Credit to Family Members Through Family Sharing

Before my family was set up with different Apple IDs through Family Sharing, all of their devices were under my Apple ID. All of their iTunes gift cards were credited to my Apple ID. Now every family member has their own Apple ID and we are connected through Family Sharing, is there a way to transfer iTunes store credit to their accounts? As it currently stands, I have all of the iTunes gift cards that they had recieved when we shared a single Apple ID on my account. If they were to buy something from the iTunes or App Store, their purchases would be charged to my credit card. If you have a solution to how to divide up the iTunes credit between accounts in Family Sharing or how to get around their purchases being charged to my credit card, it would be greatly appriciated!