Run! Yeap, I'm dead serious. Victoria's come down a bit now, but I still let her run around the place. My opinion is, I'd rather her going crazy at the airport than in the airplane. And I run with her, we race, I chase her, we watch airplanes, I don't really care what we do, as long as she is wasting all of her energy.
When I get to an airport, I like to check-in and go through security straight away, get it out of the way, then hang out where the gates are. Usually if the flight is international and direct, you have lots of shops and restaurants and depending on the airport, you have lots more options.
Once we are through, we usually have a look around the shops, we eat some food, and hang out.
Remember, it's a trip, let them explore the airport, walk, run, play. They are already excited for the trip, so let them do what they want (yes, of course, with limits). It will pay off in the airplane :-)