With everything running on credit/debit cards these days, it can be difficult to figure out what to do if you're paying cash, but here's how you can do it at Disney World.
If you do not utilize online check-in and you tell Disney that you don't want that card used for incidental charges, you should be able to pay cash without them charging your card on file.
In addition, Disney will ask you for a card to use for room charges.
Lots of people don't realize that when you charge to your room those charges aren't immediately placed against your card. Instead, charges are held until you've reached a set limit ($1500 for Value and Moderate level resorts and $2000 for Deluxe level resorts).
If you do use your MagicBand to charge to your room but don't want the card on file to be charged, then you'll need to head to the front desk to pay off the balance periodically to make sure they don't charge you automatically. Be sure to do that at least 24 hours before checkout to catch the last batch of charges before you leave.