Something to think of is trying to avoid the bigger cities during rush hour. We got stuck in rush hour coming home going through Windsor (so traffic from out west of Syd going into Syd in the morning), didn't think about it! No advice of where to stop tho.
Another idea is to have an in car DVD player. We just did a 9hr cross NSW drive and the DVD player was a godsend. We managed to do a 3hr drive, stop, 2 hr drive, stop and 2hr drive, before Lily puked in the car and we had to stop overnight, lol! The kids were angels until then and only Liam complained on the last 2 hr stretch a little bit.