I run a small childrens party business (well am starting to run

) Any way have you thought of CDs? Have your daughter pick her favorites off CDs or MP3s you already have and burn them on to CDs for the girls then just print out your liner notes on some pretty paper and label the CD with a pretty colored sharpie. It is really pretty cheap for blank CDs and some jewel cases and every time I have done this they are HUGE hits. The little girls I nanny for also have several they have gotten from other parties and love listening to them (and the ones from their parties) over and over again. I love it because it is something that can be enjoyed for a long time.
Some other ideas might be
Ribbon Dancers, Wind really long strings of ribbon around a dowel (glue at top and bottom) Leave long long long tails. Very gymnasty and so much fun.
Buy bulk sweat wrist bands and bulk patches (Micheal's has them in tubs) and combine to make customized ones!
Water bottles, Fill with a few candies, stickers, and some of those drink mix tubes (Koolaide, crystal light etc...) Then Write the name of each girl in glittery paint or let them decorate with stickers.
Do little stationary sets, Print out themed paper at home, get a bulk pack of glitter pens or neat pencils to divide up and some stickers and colorful envelopes.
Print out coloring sheets and make your own books then pair with a box of crayons (or make crayon rolls) Kids love those coloring sheets and you can customize them to your theme.
Make a craft pack, Choose a simple craft and pack it up in a pretty bag for each girl to do at home. Something like pretty beads and string to make their own necklace and bracelet.
Or Have your daughter pick out some beads she likes and you can make bracelets and necklaces for all the girls, this could be very cheap and I bet they would Love them.
You could also make Hair bows or ponytail holders for the girls