I like the travel tips posted and have a few others: before you fly with children around ages 9-13: make a check list for your children of things that need to be packed in their suitcase - have them do their own selecting and packing - then go through it with them, congratulating them on the good job they did (and making any necessary changes!)- this helps them become better and more helpful travelers!
Also, buy a few small surprise things ahead of time, like a magazine, pack of gum or small candy they like, etc. so they have something new and fun in case of delays! I also pack a few small bags of mini muffins and grapes/bananas in case we leave for the airport before they are fully awake and aware of the fact that they are hungry!