Almost every place in WDW accepts credit cards. Some of the carts may not be hooked up to a phone line yet so in this situation they only take cash. I know WDW was working to get all the carts to accept credit cards but I don't know if they have completed this as yet.
What I do is at check-in have a credit card attached to my room key (which is also my park ticket). This way one card does three jobs and it's less to carry around and worry about losing. You will be asked at check-in if you want to do this. It's very easy and convenient. You can get a print-out anytime of all the charges placed against your card. At check-out you will receive a complete listing.