When you check in at your Disney resort the Cast Member will ask you if you want the charging privileges on your room key. The CM will then ask you for a major credit card and will encode that info into the Disney computer system. You can now use your room key to charge meals, souvenirs, anything you like within WDW. You can get a print out from your resort front desk anytime. You will also get a complete print out when you check out. If you choose express check out this will be in an envelope hanging on your room very early the morning of your last day. I believe the Value resorts let you charge up to $500, the Moderates up to $1,000 and the Deluxes up to $1,500. When you reach the limit the computer system will automatically send the charge to your credit card company and you will be back to zero. Very convenient, we use this option every trip. Using this allows you to take very little cash with you to the parks. Some of the carts around the parks may still not be able to take the cards as they need a telephone connection.
Every other place within WDW will take your card with no problem....just make sure you sign the back before you use it.
ps....I have also read where people give cash to the front desk at check in instead of a credit card. Another option is to give a credit card but pay by cash before the charge is sent to the cc company.