As far as I know,you can use your card-key for charges on purchases throughout Disney.I have not used this option myself,but I did read some info about it last year in the room,AllStar Music.I believe you can charge up to a certain amount and then you may have to pay some to be able to charge again.As I said,I read some info but chose not to use this option,so some of my info may not be accurate.I may check it out further this year,in October,when we arrive.But here's a tip:If you do not charge anything to your room account and if you pay in full at check-in,at your check-out time,in the early morning hours,someone will hang a copy of your room charges on your door;and with no extra charges,you do not have to check out at the front desk.You can leave by check-out time.
Hope I've helped.