Waaaaay back in the low-tech dark ages my mother would buy me a few brand new puzzle/coloring/activity books that I wasn't allowed to touch until at the airport/on the plane. (The kind with several different types of games held my interest the longest.) She would also only allow comic books for planes. Knowing that they were brand-new and a special treat for the plane made it kind of fun. I seem to remember one flight that also came with a thing of silly putty. I thought it was great, don't have any idea how the FA's felt about it....

Plus, I've always been a reader, so that probably helped my mom deal with me more easily. With that thought, how about Harry Potter books if (somehow) they haven't read them yet? THEY'LL certainly kill a few hours!

However, as a very much "grown-up" fellow traveler now, I'm actually more in favor of finding ways of encouraging them to work off as much energy BEFORE they get on the plane as possible to reduce the squirming & kicking that kids being kids can't really help doing.