I always made sure that each child had his/her own small bag with snacks, paper and crayons, and other age appropriate entertainment options.
ALWAYS pack meals for the kids - even if the food served is something your kids are willing to eat, it is unlikely to be served on their schedule. Don't worry too much about a balanced diet, just make sure that there are healthy choices that your kids enjoy.
One person (parent) should be in charge of all the documents, to make sure that nothing gets forgotten. I like keeping them in a dedicated fanny pack.
Explain to your kids what happens when they go through security, and possibly stand with them on the side for a moment to let them see other people going through.
Try melantonin for getting over stimulated kids to sleep.