Thanks for all of the replies. This is great information. Port Douglas it is! As it turns out, I might have 2 extra days to play with to see NZ anyway. My trip would look like this:
Sydney 4 days (definitely doing the bridgewalk!)
Great Barrier Reef 4 days
New Zealand 2 days
It sounds like Queenstown is the place to go with only 2 days in NZ. I do like the outdoor activities over a "scaled down Sydney"