If you enable room charging, you can charge anything to your KTTW card at any Disney-owned shop, store, cart, kiosk, restaurant, or eatery at WDW, as long as it has a card reader.
Non-Disney places, such as those at the Swan and Dolphin, and a bunch of stores at the West Side, will not accept KTTW cards or Disney Dollars.
Note: You must specifically enable room chargin on your KTTW cards when you check in. You can either swipe a credit card, or put down cash/travellers checks/Disney Dollars/Disney Gift Card as a deposit. The charge limit will depend on the category resort where you're staying - Value resorts get a $500 limit, Moderate resorts get a $1000 limit, and Deluxe and above get a $1500 limit.