You will be able to use any form of payment that you would use in the rest of the Walt Disney World Resort. (Credit Cards, Room Keys... )
I personally never have cash on me!
Actually, a few of the carts only take cash. Learned that the hard way. Stood in line in the hot sun with just my card on me to get a snack on the DDP. Got up there, and was told 'cash only'. Also true at Arctic Dots.
So, be safe, take some cash.
(Artic dots are like $3-$4)
and if you want to have a few bucks on you at Typhoon Lagoon........try the mini donuts .....they are just like my grandmother used to make....delicious and always warm.....