We go out to eat about once a week or so and sadly it is after 30 minutes of the "I don't know, what do you want for dinner?" conversation, so by the time we actually get in the car, it is right in the middle of the busy dinner rush. My kids are over the 2 crayons and coloring page that some restaurants give, so I have my own stash. I keep a small diaper bag packed in the car with these things...
Office dot stickers...you can get these just about anywhere. My kids love to make caterpillars, snowmen, and as a family, we have been known to give our dinner order with one on our noses.
Play dough...you know the little size. They like to "make" their dinner out of it.
The last thing we LOVE are the sticker scenes you can get at Oriental Trading Company It comes with a scene and a sheet of stickers to put in the scene. This example is an ocean scene and then a sheet of stickers that help you decorate the scene.
These things make waiting for dinner a lot less hairy and we are all usually involved with the activities, so it is fun to interact and by the time the food comes, we aren't ready to pull our hair out. :)