Have a look at this site. It has inexpensive ideas for entertaining children, and travelling in the car is included.

http://www.ideas-to-save-money.com/e...activities.php

How about cards like Go Fish, or Old Maid? The 9 year old might like that. How old is the younger child? Maybe we can help think of other things for you.

Maybe you might find more by doing a web search for activities for children in the car.