S.H.
My daughter is 6.... but at that age, my girl liked making things.
How about, going to your local garden store and picking up some cheap generic (unglazed) terracotta/pottery flower pots... have the kids paint it... and then they can fill it with dirt and some kind of flower seed.... sunflowers, Zinnias, Marigolds, beans are easy to grow. Or a radish seed. Something fun.
Or, go to www.orientaltrading.com and they have TONS of cheap party things for any age, games too, and craft stuff, and goody bags etc.
Also, they can paint each other's faces, with tempura paint.
And then do a group photo of themselves as a memento.
Or, get a huge poster board, and have written on it "Sally's 5th Birthday" (or something like that), and then have all the kids put their hand-prints on it with their name, and then it will be a nice souvenir for your daughter and she can even hang it in her room.
And, kids always like treasure hunts... just get a bunch of cheap girly "jewelry" or something, hide it around your yard, and let them find it. Giving them each a brown paper bag that they can write their own names on.
Good luck,
Susan