I will say that it is imperative to have a strict itinery to keep the girls occupied. I would also enlist the help of a few other adults.
My daughter had a "spa" party theme to her 9th birthday. As we were planning an overnight party we had the girls show up around 5:00 PM. As the girls arrived they were directed to the sun porch where karaoke was set up and the girls socialized for about 1/2 hour before being escorted into the "spa". We had a few snacks available there "tea sandwichs"
We set up one room for the "spa". We placed folding chairs in a semi circle and lined shelves with nail polish, facial creams, toners, white towels, etc. We had scented candles a small indoor fountain and mood music. We also purchased a roll of tulle fabric and draped it around the room (keep away from open flame)We also purchased some pre teen magazines (American girl, etc. for them to read)
we had approximately one adult for each two girls. (a few of the mom's stayed to help but left later) The party started by girls applying facial cream to their faces (we purchased a very mild one from a spa party store.) (we had also hung a long mirror sideways on the wall so they could all see themselves to apply the cream) After they applied their face cream, the girls sat down and soaked their feet. (we purchased white dish pans and put in warm water and scented salts.) We had purchased very inexpensive pedicure sets from a party store. While the girls soaked we applied cucumber slices to their eyes and performed hand massages. Then we dried their feet and gave them a foot massage and pedicure. They were able to choose from a variety of cool nail polish colors. Finally, the girls were offered warm, white face cloths on a tray to remove their face cream and applied a moisturizer. We had a small hamper ready for the towels and face cloths. Each pedicure set came with cheap flip flops so they girls wore them after the pedicure and we went into the kitchen for pizza and soda.
After dinner we had the cake and presents. My daughter's birthday was in July so it did not get dark until late but by the time they were through with the presents it was quite dark so we headed outside for a night time scavenger hunt. (We live in a quiet neighborhood which used to be a summer vacation area so it is safe to travel around at night) I had marked each new clue with glow sticks, bracelets or necklaces which they were able to decorated themselves with. The final prize was candies, popcorn and movies.
When we returned to the house the girls did a project of make your own scented body lotion, lip gloss, body spray (also purchased from the online party store)
Before bed the girls decorated a small memory quilt which we purchased at Joann Fabrics. It came with fabric crayons, each girl decorated a square with a fabric crayon which is set by placing a piece of paper over the fabric and ironing. My daughter still loves her quilt!
This kept us occupied to about 10PM and then we set them up with their sleeping bags and pillows to watch movies and have snacks. (I will be honest, their were a few who stayed up until 3:00 AM)
In the morning breakfast was a yogurt bar: we placed out ice cream bowls and the girls could choose between strawberry or vanilla yogurt placed in large bowls and then add a variety of toppings. (dry cereals of various types) We also served juice in plasic wine glasses and fresh fruit and muffins.
Everyone left with their pedicure set and make your own lotions as their goody bag.
I will say the party was a success, though I was exhausted!
The web site where I purchased most of my supplies was thebirthdayboutique.com I was very satisfied with the service, products and price.