Heron Island is a great place to snorkel the reef, it does take some time to get there. Usually you take at 6 AM flight from Sydney to Brisbane (1.5 hours), then a flight to Gladstone (1 hour) and then there's a two to three hour ferry ride out to the island. It's magic when you get there. The price varies a lot depending on the season, but it usually includes all meals. The cheapest rooms, the turtle rooms, are fine.

Uluru doesn't need 4 days, 2 days and one night would be enough. There's only two things to see: Uluru and Kata Tjuta (Olgas). Walking around Uluru takes about 4 hours and then there's walks through Kata Tjuta that take about 2 hours. It's another expensive location as the food has to be shipped in. Alice Springs and Palm Valley are the other places to visit in the Red Centre, if you did want to spend longer.

What you do, always depends on what you have already done. If you have been to tropical islands before, they are all much the same.

Ayers Rock is truly unique though. I recommend climbing it. Others will not. It is entirely your choice, if it is open. You will need at least two hours to climb it. More if you want to explore the top. I took five hours with three or more exploring the top to the far end and back. It is like no where else I've been

The Olgas too, are brilliant and only take a few hours to do the long walk. The short walk is less than an hour and easy.

Most tourists only spend 1.6 days at Ayers Rock NP. Basically fly in do the two rocky bits and fly out again.

For twelve days:-
Sydney (1-3days) - Friends (1-2days) - fly to Ayers Rock (2-3days) - fly to Cairns ( 5or so days) - fly Home. Would be doable.

Cairns has an international airport. It is also cloesest to the reef and has lots of other things to do.

I can't comment on Kakadu and Heron Is. having not been to either.

You could slip in Kakadu but you will be rushed. Or don't do anything in Sydney unless there is really a "Not to be missed" on your list. Or kill two birds with one stone and do things in sydney with your friends.

PS Ayers rock will be hot in November 30Cor so. But if you take care and drink lots and wear a hat etc. you will be OK.

AC plane to AC hotel to AC bus to rock. EASY.

"If you have been to tropical islands before, they are all much the same." Sorry Peter, I beg to differ - I've been to a number of tropical islands, and Heron Island is not your typical tropical island. There are few places like it in the world, in the way of resort islands anyway.

Yes the Northern Territory will be getting very hot in November. I love the Red Center, but it seems like a lot of time and effort to go there just to see Uluru and the Olgas over a day or two. I'd leave it for another trip when you can spend a little more time to see more of the Red Center at a more pleasant time of year (i.e., May-August).

My suggestion would be Southeast Queensland in November - in particular Heron Island and Fraser Island, which would complement Heron nicely. 7-10 days in the region would be perfect - would recommend at least 3 nights on Heron, same for Fraser.

I would also suggest Queensland for November. I have been to Kakadu, Uluru, Alice Springs and Kings Canyon in July with temperatures then of around 28 - 30 degrees Celcius and low humidity. As the year goes on the temperaturea get hotter and higher humidity makes it quite uncomfortable if you are not used to it. I would certainly recommend a return visit in June to August to visit the Northern Territory - another interesting area of Australia.
Queensland is also quite a diverse area which I have been to twice, and look forward to returning to. I would concentrate on South-east Queensland as RalphR suggests - you have a mixture of sea, forest and wildlife to enjoy. Perhaps a couple of days in Sydney with your friend before you fly home would be a good way to end a busy 10 days.

Whatever you do, enjoy Australia.

Thanks, your comments help me a lot. I've concluded that we'll need to leave Kakadu for another trip.

We enjoy desert heat very much, we live in California and have been to Death Valley in July! My friend is suggesting flying into Alice Springs and seeing some canyons and gorges along the way, itinerary suggestions for 4-5 days would be welcome.

I can't make the flight connections to and from Gladstone fit very well and I don't want to be backtracking to Sydney, so I'm not sure yet if Heron Island will fit though it does look lovely.

If you can spare 5 nights in the Alice Springs area you could fit at least one full day in Alice Springs.

Fly into Alice Springs - I seem to remember the plane arrives from Sydney about 2:00pm -ish - spend the afternoon at the Alice Springs Desert Park, then the next day take a tour to Palm Valley; or drive out to Glen Helen Lodge West MacDonells, and stop at all the cool little places on the way back - Standley Chasm (best time to be there is midday), Simpsons Gap, Ormiston Gorge, etc; or out to Trephina Gorge in the East MacDonells.
Next day travel to Kings Canyon, either in tour or driving yourself, explore Kings Canyon and stay somewhere in the area.
Third day travel down to Uluru, again driving yourself or picking up a passing tour bus. Visit Kata Tjuta in the afternoon and watch sunset at Uluru. Next day for sunrise at either Uluru or if you have your own car sunrise at Kata Tjuta. Then spend the day exploring either or both place/s, and sunset at Uluru or Kata Tjuta if you have a car.
Last day fly from Uluru to your next destination. Or you could do the trip in reverse.
Oops, just realised this itinerary takes up 6 days. However, it does give you a general idea of the Alice Springs area.
Dot

Alice Springs is a great place to visit. Along with Dotty's fab suggestions above I'd also add the Desert Park, which is a real highlight with lots of nocturnal animals and well-laid out habitats. http://www.alicespringsdesertpark.com.au/

Also of interest is Araluen Cultural Centre which holds the largest collection of works by indigenous artist Albert Namatjira http://www.araluenartscentre.nt.gov.au/

The Olive Pink Botanic Garden is another place of interest, she was an early supporter of indigenous rights.

Papunya Tula is where the Western Desert Aboriginal art movement began, they have a gallery in Alice Springs where you can view current art.

http://www.papunyatula.com.au/

And while on the subject of indigenous culture, I'd suggest you read this before visiting Uluru, it's a request from the traditional Aboriginal owners not to climb the rock, which is sacred to the Anangu people:

http://www.environment.gov.au/parks/uluru/explore/do-not-climb.html

I heartily endorse Dotty & Susan7's votes for Alice Springs.

If you can stretch to it. I'd fly Sydney - Alice Springs. Stay 2 nights then take a 1 way tour or fly to Uluru. If you get there mid afternoon, go to the Cultural Centre, watch sunset and go back before sunrise to see it strike the facets of Uluru. Walk around it (9 kms). If its not too hot - go across to Kata Tjuta & do a walk or two there. If it's too hot by the time you leave Uluru, leave it until late afternoon - but don't walk in the dusk/ dark.

I love Kakadu, but I think you're likely to run into the Wet in November. Next time!

Have fun & thanks for coming to visit our beautiful country.

Sigh. I'm a Sydney-sider and biased. LOVE Sydney. It sounds like your friends are in the southern highlands, beautiful country. Things you must do: the Bridge Climb - I hate heights, but it is absolutely amazing and very safe, try for a sunset climb, you get the best of both worlds. A tour of the Opera House, a trip to Taronga Zoo, a ride on the Manly Ferry (especially if the seas are high). Find some time to head into Newtown for great restaurants. Snorkel Fairy Bower (near Manly) catch the sea plane up to Cottage Point or just fly over the harbour. Depending on how much time (and money) you really have. Sydney is not cheap, but look for discount vouchers (Spreets and Livingsocial to mention a couple)to see what you can buy ahead. Chinatown in Sydney is bigger (and in my view better) than San Francisco. Nothing like the culture in the red centre though, it depends entirely on what you want to do. Spend a day in the Blue Mountains (west of Sydney and easily accessible by train and bus tour), check out the scenery and the colours.