Australia Honeymoon 3wks December

My Fiancee and I are looking at Australia for our Honeymoon for three weeks in December. We were initially considering adding New Zealand or Tasmania but right now we're thinking of the following itinerary. Please provide feedback on anything like logistics, weather, recommendations as we are in the USA and have no clue about what to expect.

We enjoy exploring cities, food/bars/nightlife, gorgeous nature, animal encounters and have loved our recent travels in Europe.

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~Dec 11: Fly into Mel from USA

3 days in Melbourne (recover from jetlag, explore the city and do Great Ocean Road one of the days)

3-4 days Adelaide (A day in Barossa?, A day on kangaroo island or overnight, and explore Adelaide)

3-4 days in Cairns (One day Great Barrier Reef, exploring Palm Dove/Point Douglas, Daintree)

1-2 days in Brisbane with animal sanctuary and as a natural layover before Whitsunday

3 days in Whitsunday (we figure this is a good place for Christmas as cities are mostly closed for holiday?)

end of December (~12/28-1/2) in Sydney for 4-5 days to experience NYE, blue mountains, beaches.

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As you can see, there is no outback (as I've been told it's too ridiculously hot) but I have left Cairns/Whitsunday even though I've been told it's stinger season. With that said, is there a point to go to Cairns/Whitsunday if we can't even swim or go in the water without a suit? It looks gorgeous and I'd love to keep it but don't want horrible weather/dangerous conditions to stop us from even enjoying it vs another option (like Tasmania).