We used to play 'Who Am I' a lot.
You think of someone famous and not too obscure, and the others in the car have to ask you questions that can be answered yes or no. Officially, they are out if they guess wrongly, but we used to waive that rule depending on the age of the children.
We also played The Animal Game, where you take it in turns to name an animal beginning with the next letter of the alphabet, so Anteater, Bear, Cow, etc. That one can be adapted to countries, songs, anything you like, really.
You will lose the will to live, but the children will probably enjoy it.