My tip is done before you get on the plane. Give each child a little flying bag. It can be just a gift bag or something more sturdy that you can close up so you don't lose the contents. They can decorate it with pictures that relate to the trip they are going on. Have the child put some of their favorite small toys in it and let them pick several snacks and a juice box. You can include something new like a book or drawing materials to make it special. This can also be their responsibility to keep track of, a good learning lesson.