yes you can! You can even use them for room only charging they will take the balance off the cards and put it on your room instead of a credit card...
I have to say I love the disney gift cards... I have such a hard time saving money that for me its nice and easy to buy a 50$ gift at the grocery store everyother week then to put that 50 off to the side.. I just cashed about 250$ in gift cards against the balance of my trip in december online
plus buying them at the grocery you get the gas perks.. except the last time i went the girl wouldn't do it i think because her manager was bagging my groceries she had to purchase them in a seperate transaction which was kinda a bummer since i bought a $100 gift card and spend $50 in groceries