I visited Australia and New Zealand and spent about 5 weeks in each. I drove myself, camped quite a bit, stayed with various friends and family, and I haven't been to Fiji or PNG. With that in mind, these are my suggestions: Check the weather, they're heading in to summer. I believe there are more restrictions to swimming in the ocean off cairns and other places up north during the summer - so check that out. It may mean it would be better to focus on Melbourne - Sydney - Byron Bay - Brisbane. The centre (Uluru) will probably be unbearably hot, so maybe worth avoiding, but again check the seasonal weather. There is some great hiking in the blue mountains. The coast along from Melbourne is very nice, and Melbourne is a full-on foody city. There's plenty of surfing around as well, which is great fun if you haven't tried it.

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