Driving on the left side is a bit daunting, but doable. There is really no reason to waste money on tours in Australia. When I was in Melbourne (years ago granted) I think we had a car and just went when the penguins were supposed to come ashore. I didn't see how old the children are, but if you are on a tour and they get tired or bored, you're stuck. If you're on your own, you can decide when to come and go. (I should note I hate tours.)