J.S.
Have you thought about having it in your house? You can have a 'cookie decorating' party. Get slice and bake sugar cookies, make round circle cookies ahead of time. Then get the icing and decorating candies and the girls can go wild decorating. Favors could be an apron with their name on it (they are only about $2/each at Michaels) or the cookies themselves wrapped in pretty clear bags w/curly ribbon. Works well with cupcakes to decorate also and then you don't have to have a birthday 'cake' separately!