We've done a heap of driving with the kids. We try and time it so sleep time is soon after we leave, stop after 2 1/2 to 3 hours when Lucie wakes for something to eat and a quick play in a park (and feed Ned!) and then another 2 1/2 to 3 hour stint. It works pretty well - I usually sit in the back between the kids and play with Lucie if she starts getting bored. I just take a bag with some toys she hasn't seen for a while and snacks, make sure I have plenty of water for her too and we are usually all pretty happy!