Colorforms stuck on the window are good. Play bingo with cards you made ahead of time with things like "cement mixer, farm, cows, red VW Beetle, stop sign, schoolbus, man driving while wearing a hat, skyscraper, etc." you know, things you're likely to see, and the kids can cross off what they see until someone gets Bingo. That was a great one for long trips for us! Play The Map Game, if they're old enough. One person picks out a town on the map, the other has to find it. The little, obscure towns are hard to find and will keep the other kid busy for a long time! Play a game called "Fortunately": One person starts with something like: "The dog ate my homework." The next person starts with "Fortunately..." and adds something that makes sense, like "Fortunately, it was early and I had enough time to re-do it." The next person continues, but with "Unfortunately...." like, "Unfortunately, my pen ran out of ink." And you keep alternating with statements that begin with "fortunately..." and "unfortunately..." Eventually it ends, and it takes a long time, and it's fun!!
We got a million of 'em.....