Keep the weather in mind. Queensland is better to visit in winter, not in peak summer heat. For 2 weeks you have just enough time to see both Sydney and Melbourne properly -- these are huge cities, of about 50 miles radius, with a lot of interesting areas far from the city center. If you really want to see someplace different, consider Kangaroo Island, Adelaide, Tasmania. Really no time for NZ and best to stay away from the hot parts (e.g. Uluru) unless you know what you are getting into. Melbourne is a wonderful city if you have locals to show you around (the best parts are a bit hard to find for tourists).