We've used my daughter's cast member discount on room reservations many times and there has never been a problem using my credit card at check in. For meals and merchandise - yes the cast member is supposed to pay. We were in
Disneyland last summer and when paying for a meal a manager happened to be standing by the register and saw my daughter going through her wallet looking for money and joked that he wouldn't have a problem if "mom" paid! But then two weeks ago at Animal Kingdom my daughter was buying a shirt and I had her cash in my purse and the cashier started giving us some attitude. I told her the cash was my daughters but she still lectured us. I didn't even hand her the money. I gave it to my daughter who handed it to her.