I just packed:

a "train stations of great Brittain" colouring book
Madlibs
magnetic tic-tac-toe and checkers
Mazes
a pile of books

I'm going to be watching for more replies. My kids are aweseme on planes and trains, but Carseats are hell on wheels. (literally)

DS1: Hon, you already finished your homework
DS2: Quit it with the protesting already!