Sleep over party with movies, popcorn, make your own hot fudge sundaes, music, pajama dancing. I remember my daughter at that age, she wanted all her parties to be slumber parties. We had Mexican themed party with Cinco de Mayo decorations and Mexican food. We had a Hawaiian Luau decorations and food. We had a Japanese Sushi party decoration and all. The sushi party was when she was a bit older than 10. You might look at Oriental Trading for some ideas for themes and the prices for the decorations are very good there. The have great customer service as well. I have been ordering from them for personal and business needs for several years.
I had one year when I bought straw hats and dollar store flowers, feathers, ribbons and all kinds of things to make fancy hats and then we had a photo shoot and we burned cds for all the kids and parents as favors. It was a blast and the kids had a blast and to this day, the kids are still talking about the fun they had at the party. They were around 9 or 10.
Let me know if I can help you with any more information on these ideas...