Which could be nothing:). But what about photography or movie making ( if you have a camcorder you would be comfortable with them using ). My two are girls also, but are only 10 and 7. However my oldest really loves photography and what works well for us is she can work on it herself doing nature photos or using photoshop elements on the computer. BUT she also has a very willing model in little sister so this can keep them busy doing something together. I don't know if that would be something your girls would enjoy or not. My girls also would like to make movies, but I really haven't let them mess with the camcorder yet.
My girls also enter lots of things in our county fair - from crafts and photographs to baked goods - and that seems to give mine something to work towards with their hobbies ( my youngest loves to cook ). Whether they are trying new recipes or a new craft, coming up for ideas for the next year's fair entries keeps them trying different things, and it is a great way to figure out what they like and don't like.