I've done NSW-WA a few times now. With & without a DVD player - I definitely prefer with! - with new movies they haven't seen yet, so they didn't get too bored. Colouring books & pencils, diaries for the older girls to write where we'd been & what we'd seen that day (5-6 day trip with 1 driver). I loaded up on apps/games on my ipod & phone too.

I used the pocket things you hang on the back of the front seats, so everything was in reach. Plenty still ended up on the floor, but it makes life easier. Mine also collected bits & pieces at different stops too. Sometimes just a rock, or stick... or a lizard spine :/ but that gave them something to play with til the next stop. We left the 'booby book' at the rest area it was found at though...

Its very different crossing a desert though, the more to entertain them the better!