First does she have her own seat or not? If she does, bring her carseat for her to sit and nap. DD flies incredibly well and I'm always overly prepared. We have her favorite blanket, new and old books, new toys, paper and few pens. DD started to draw at that age so maybe it would work for your DD. Lot of snacks. I second stickers, she is so young maybe try to find really big ones and easy to peel like wall stickers. Absolutely try to have her watch DVDs, maybe something with songs like Barney. She would not have to understand what is happening to enjoy it.
