If you are relying on DC power ports, I would call Qantas and ask. I am sure that they can also describe or send you to a web page that describes the in flight amenities like power supply, in flight entertainment and the like.

In the 80's and 90's I did a lot of travel from SFO to SYD and Perth. Long is right, mate! Then there were no power ports in business as I remember. Certainly in coach I took an extra fully charged battery for my computer. Lots of CDs. No DVDs in those days.

Two other suggestions: books and sleeping pills!

Enjoy your time on that fabulous continent!