Print coloring pages from the web and color some and glue to posterboard, Cut them out and hang from the ceiling for decorations. You can also have a coloring contest with some. Also, if you have a friend who can draw, have them draw a large Cinderella for a game of "Pin the slipper on Cinderella".
That's 2 games and decorations for only about 5 dollars. If you want prizes, you can buy party prize packs at a dollar store, you get about 4 prizes for a dollar. These tips can also be used for almost any cartoon or book your child loves. Hot dogs make a cheap child friendly party food.
Great Ideas. Also, if the friend that can draw would draw another Cinderella, w/o the face, just the hair and cut a circle from the face, the girls could hold it up in front of them, and put their faces in the hole to have a digital photo taken. This can be printed at a later date by the birthday girl to be sent with "Thank You" notes (never too early to teach it is always nice to say "Thank You".