We used to drive to and from Queensland when I was a kid a few times a year to see family...LOVED it! lol
We weren't as little as yours though...
Personally I would rather drive than fly and you can see the things along the way.

Oh, and FYI - Dubbo Maccas is the best place to stop for breakfast - best McDs breakkie going - and they also happen to have the BEST chocolate thickshakes in the country lol true story!!