We are also using gift cards and I think it is smart. We save all year by buying a gift card every week and then use them to pay for our extra expenses. Of course you keep track of them like you would any form of payment. Each person does what works for them. I don't want to use a credit card or have a balance when we are finished with our vacation.
I don't think gift cards are smart because why trade in cash money that is good anywhere in the U.S. for anything you want for cards that are only good at Disney? Cash and/or gift cards can get lost and/or stolen and have little security.
If I save my money in a savings account before vacation and accrue interest, then work within my budget on vacation, then use my credit card to pay my room balance, then use my savings money to pay my credit card bill then I have (1) had my money in a secure place (2) Had access to my money if say my Disney vacation had to be cancelled (3) earned interest on my money while I waited for the credit card bill (4) earned rewards on my credit card (5) I haven't had to go around buying multiple gift cards and stashing them away and I don't have to stand in line at check out watching the CM ring up a bunch of gift cards