Crafts are always fun. You could make sock animals, all you need are some hot glue guns, knee socks, stuffing and googly eyes. Yarn and felt are good too for decoration purposes.
Decorate your own little planter, and buy potting soil and plants to go in the planter afterwards.
If your neighborhood is amenable, you could send them on a scavenger hunt.
I don't think you'll need too many activities. Girls this age are pretty good about keeping themselves entertained.
I was thinking about having them make candy kabobs since it is an activity and would also serve as the goody bags
That actually sounds like fun. I think I'm going to make lipstick with my DDs this weekend. I can just see how showing them how to make their own stuff could open their eyes to the possibilities. Next thing you know one of them will come back with all her own products... Have a good party, your DD is gonna be thrilled no matter what.
Just a word on the candy kabobs. I made those once as a prize for my piano students. They're harder to make than they look! The gummy candies get all stuck to the stick as you're trying to slide them on, and leave gummy gunk behind all along the stick... then the other candies won't slide on very easily at all. The piano students loved them but I won't be making them again!
ETA re. the crafts. My friend taught a group of pre-teens how to make (hand sew) their own "cute monster" stuffies, and all the kids really enjoyed doing it.
I think you're right to have planned activities. My daughter just had her 9th bday party, and wanted it very open - dinner outside, bonfire w/smores, flashlight tag, dancing to their music, we set up a tent outside and they hung around and talked. but.... my daughter knew what she wanted, but didn't know how to keep the others on it - and I tried not to micromanage, so she ended up being upset when the party went in another direction and girl bickering ensued. they actually weren't ready for the unscheduled sort of party that adults have, as much as she wanted it - and i knew all these girls and thought they could do it. the scavenger hunt is a great idea and they love working in groups. have fun!