I think there used to be a few snack carts that also didn't take gift cards. If I remember correctly, when we were at Epcot my daughter, her friend and I got henna tattoos and they wouldn't take it there, but I believe we were able to put it on the room charge and if I'm not mistaken, you can pay off your room charge with a gift card before you check out.
We do the same thing and buy gift cards little by little so that when we go it's not such a huge out of pocket expense. You can also reload the same gift card multiple times so that you don't have too many gift cards floating around. I have 3 going with different amounts so that when we go I can give me teen daughter one to have for spending, and then have 2 others with larger amounts for my husband and I for food, etc.