I have booked a 3 wk vacation to Eastern Australia over Christmas this year. My in-continent flights are confirmed, and Hayman Island resort is non-cancellable. Any other accommodation can be changed, and I haven't picked accommodation for Noosa yet. I would appreciate any comments on the itinerary or accommodation.

Our group includes 2 adults, 2 girls (14 and 16) and 2 boys (8 and 13).

What we have booked is as follows:
Sydney: 4 days (starting Dec 20) at Quay West Suites Sydney (at the Rocks), in 2, 1 bdrms; booked Rolf Harris at the Opera House, will book the Bridgeclimb; will see the Zoo; considering going to Jenolan Caves;
Hayman: 4 days (2 hotel rooms), I assume that one day will be some sort of snorkel tour to the reef;
Port Douglas: 4 days: have a 3 bdrm at the Sheraton Mirage; will book a Kuranda Day Trip, perhaps Cape Tribulation and perhaps White Water Rafting:
Noosa: 4 days: considering 2, 1 bdrms at the Sheraton; surf lessons, will book a Fraser Island Day Trip
Sydney 3 days: 2 bdrm at Quay West Suites: go to Manly or Bondi beach

Thanks for your comments.

we were in Sydney/Port Doglas for Christmas last year. Consider Tonys tropical tours for a trip to Cape Trib.. fantastic day out. We also did a snorkel trip with Wavelength FAB.
Sydney was also fantastic am very envious

I hope you are in Sydney on New Years Eve for the brilliant fireworks display on Sydney Harbour.

For days for Noosa is more than I would have booked. You should stay at Hervey Bay to access the Fraser Island tours (assuming that is what you want to do) rather than Noosa.

They call Hervey Bay "God's Waiting Room" and it is so, so true! Try to book an overnight stay on Fraser Island if you don't want to spend so much time in Noosa. But I'd pick Noosa over Hervey Bay even if it is much farther to Fraser.

Quay West Suites in Sydney is great. It's worth the extra money to try and book a room with a view of the Bridge & Opera House - especially if you are there when they have fireworks.

For snorkeling/sailing from Port Douglas, try shaolinportdouglas.com - so much better than the big operators that take hundreds out to snorkel on the high speed boats.

Your trip sounds awesome...and very similar to what we did this past March with 2 adults and 2 teens. If you are interested, look up my trip reports. (including Hayman).