Is it a Minnie Mouse themed party? You might want to try and find Mouse based crafts. I'd got to
Walmart, Joanns, Michaels some place like that and find some kid friendly (cleanup friendly too

) ideas you can modify to fit a Minnie Mouse party. I'd pick up the foam craft paper and cut it into different sized circles, Like one big circle for the head, two medium sized ones for ears, two small ones for eyes, one for the nose...etc then let them glue them together, or you glue them they get to decorate their own mouse....
Another idea... collect a bunch of different sized little boxes, (small shipping boxes, etc) from around your house. (Or call a grocery store and tell them you need small boxes and ask if you can have some of their old ones if you come pick them up.) The take your craft box, (if you have one if not bring together scraps of fabrics, old scrapbook paper, markers, crayons, anything of this type) and let the girls decorate their own "Mouse House." If I were you I'd make one before the party so they can see what you mean by a mouse house... color construction paper for the wallspaper, make a "door", tie a bit of fabric together for a bed... This suggestion is kinda strange but you could buy those little mice that cats play with, not the ones with catnip in them, and let each kid have a mouse to live in their house.
http://partysupplieshut.com/mickey-mouse/
This website has a couple cute ideas too... might be able to take some ideas from it!
Good Luck! And Happy Birthday wishes to your DD!