Don't be alarmed if adding credit cards to specific magic bands doesn't work out. It's hit or miss as to whether this will actually be done correctly, so be prepared for snafus and an inability to ever actually accomplish that.
I speak from personal experience. It was a nightmare to work out with the other family and if you've ever tried to decipher a Disney billing statement upon check out you are in for a treat.
For that reason alone I now avoid that like the plague. If we are traveling with a non family member, I insist that they or their parents provide a gift card or other type that will cover their expenses. Never again will I make repeated trips to the resort or guest services to work this out. It took up too much time of my vacation and it was extremely aggravating.
Don't do it. Trust me.
~NM