J.K.
I had a theme party for my daughter when she was 9. Shindigz.com has a great selection of party supplies for theme party. I also went to dollar tree and bought them crafts to do, we ordered pizza, had root beer floats and then a slumber party. I even made the invitations homemade. it was a great hit and the girls she invited still remember it 3 years later! Good luck and hope you have fun!
~J.