If you think the girls will be interested in meeting the characters, I recommend:
1. Doing a princess meal at DCA. All princess characters, plus some people dress up their little girls in princess outfits, so cute! (I want to just walk by before opening someday and get pictures of little girls in their dresses!)
2. You may be able to get Tink's autograph for DD9! If the girls will be doing the autograph thing, it's something to think about. My DS6 lost his first tooth in the park, and that evening while he went swimming with DH, I dashed down to the DLH front desk. I was looking for Tink's autograph (so she could be his tooth fairy), and the folks there went all out! Anyway, if your DD has an autograph book, you could bring it to the front desk for a signature, then slip it back to the room, maybe leave it out near a window with a trail of glitter leading to it? (Buy the glitter at home, though!)
Your DD probably doesn't believe like my 6yo. He doesn't really either (he was nervous about meeting the characters, so I told him they were people in costume.) But while he was meeting them, he really seemed to forget that part!

Even if he hadn't believed the Tinkerbell tooth fairy, it was a fun little surprise for him.