if your fd is under 2 and is getting a special fare or will be flying on your lap, you will need a shot record or other form of id that will serve as a proof of age. otherwise, it is wise to carry with you proof that you are the foster parent and are allowed to travel with her on this trip. it will be an official looking document, most likely signed by a judge, that you will need to ask your social worker about. no one has ever asked me for it, but i wouldn't ever want to be caught without it.
have fun on your trip!