Disney Dollars are just like cash, only with pictures of Disney characters on them rather than the US president. They're very much like Monopoly money, only with real value. Basically what you do is buy the Disney Dollars with regular money in a one-for-one trade. $1 American dollar = $1 Disney. You can use the Disney Dollars as payment for goods throughout the parks. More on this
HERE. I know that several of the Moms Panelists love Disney Dollars, but frankly they scare me a little. Because they have real value, they must be protected just like you would cash. To me, the toy-like feel of them makes it seem like you're not spending real money, which you are, and I think this would make my children less cautious about their purchases. But again, many of the moms do have their kids use Disney Dollars in the parks.
Disney also has gift cards that you could purchase for your daughter. These look more like credit cards. You load a gift card with value at the beginning of your trip and you or your daughter could use the gift card to pay for food and merchandise in the parks.
For a comparison of Disney Dollars vs. gift cards, click
HERE.