Any chance you are walkers? If so, check out the Bay of Fires walk at http://www.bayoffires.com.au/
The walk isn't at all strenuous, the beaches are the most magnificent I have ever seen (using beaches in California, Hawaii, Thailand, and Cape Cod for comparison), and the Bay of Fires Lodge is spectacular. No, it's not 5* luxury (composting toilets!), but the setting is unique.'

Almost forgot: Lizard Island is terrific, but not in January if you don't like heat!