Australia for 2 Weeks

The spots that you have picked are great BUT they are all a long way apart, Australia is huge, so you would loose 3 days travelling between the major destinations Sydney, Cairns and Adelaide. My first thoughts, have you booked your flights yet? If not look at what is sensibly available to you in terms of flying into or out of Sydney and the same for say Cairns and Melbourne and what could be combined to maximise your time enjoying Australia. Depending on your flight schedule and the number of days that you will actually have may be consider Sydney, Cairns and Melbourne as your main destinations and add day trips to see some of the surrounding area. The Blue Mountains are beautiful but given your limited time, I would just make that a day trip and also add an extra day to your stay in Sydney, there is lots to see and it is a lovely city to visit. A car is useful for Far North Queensland but there is also a very good selection of bus and boat tours from Cairns. Again I would consider adding more time in Cairns, there really is a lot to see up there. The Whitsundays are more than 600 kms (370 miles) from Cairns, so probably not this tri.. I love Adelaide (my home town), Kangaroo Island is beautiful and the Great Ocean Road is a lovely trip but again the tyranny of distance is your greatest enemy, so maybe next time. Melbourne is also a lovely city to visit and again plenty of opportunities for day trips.

A quick glance at your plans and some sums and that looks like 5000 plus miles of travel within Australia across your 2 weeks. Are you up for that?

Another thing to be aware of is that Spring school holidays are from 19 September to 10 October across the 4 states that you are travelling. Each state has 2 weeks, 3 for private schools so you could juggle where you will be to some extent, but you will find everywhere busier and more expensive than if you avoid them altogether.
I also think that in only 2 weeks, Sydney, Melbourne, Cairns & Adelaide are too much (forget Whitsundays), particularly with that road trip thrown in. You can do it but less will be more.

Cairns to Whitsundays and back is about 800 miles so I'd give that a miss.
You probably need to keep your Blue Mountains to a day trip so you can get a reasonably early flight to Cairns. It is over 3 hours flying, hotel to airport an hour before departure, airport to hotel in Cairns it's going to be most of that day.
A trip into the Daintree is 150 miles return a full day. A trip out to the reef most of a day too. As I said a trip to the Whitsunday is a miss.
Flying from Cairns to Adelaide is well over 3 hours flying. Again most of a day gone.
Adelaide to Cape Jervis is 60 to 70 miles, the ferry to KI takes 45 mins to cross. If you take a car then you need to get there with a bit of time. Takes some time to get off too so about 3 hours from Adelaide to driving off around KI. So you probably want to stay arrival night in Adelaide then head off to KI next morning.
I assume you are planning on overnighting in KI. One day or two?
What's the plan for the drive to Melbourne?
It's about 600 miles. You can go 2 different ways. Whichever way once you hit the GOR don't expect fast travelling. You might hit 40 mph if you having a great run. There are numerous points of interest though so unless you skip them it's going to be a slow journey. You probably want to not be hitting up the final run into Melbourne any later than 3 pm as you can get seriously bogged down in traffic. FYI Metro Melbourne has a population of more than 5.5 million. It's busy.
Cheers.

Thanks for all of the initial responses. Whitsundays is definately out...too far. I think the Blue Mountains for a day trip will probably also be a good idea. For Blue Mountain day trips, I'm guessing it is best to do a day trip tour out of Sydney (any recommendations??) or is it recommended to self tour for a day.

When we looked at this option for our initial plans I realize we will burn most of two days traveling between Sydney/Cairns and Cairns/Adelaide. But even if we cut out Adelaide to Melbourne, we'd still lose a day flying back to Sydney or Melbourne to return home.

What is the feeling about the fires in Victoria? I assume the fires will be out, but is there extensive damage which could cause problems in Sept/Oct?
Thanks again

The current major fire concern is the Gellibrand fire in the Otways. This is an area north of the Great Ocean Road. There is concern re areas along the Great Ocean Road but at this stage I don't think it has impacted. Fires are a common occurrence so you may well come across some areas that have been burnt over the last few years. I wouldn't let that worry you. You will be going through in Springtime and these areas will be well into their regeneration.
You have an ambitious plan and you will be covering a vast area. It is certainly very doable though.

Do Blue Mountains on day trip from Sydney.
DO NOT miss the Great Ocean Road and Penguins at Phillip Island.
Not sure Adelaide is worth it. You need more time in Sydney and Melbourne.

Something like this.
Day 1. Arrival day Sydney. Overnight Sydney.
Day 2. Sydney. Beaches etc but I think you will need 2 full days around Sydney it's a huge city. Overnight Sydney.
Day3. Sydney. Further sightseeing. Overnight Sydney.
Day 4. Daytrip to Katoomba (Blue Mountains). You can do this by train. Overnight Sydney.
Day 5. Flying Sydney to Cairns. Overnight Cairns.
Day 6. Daytrip to Great Barrier Reef. Overnight Cairns.
Day 7. Daytrip Daintree Rainforest. Overnight Cairns.
Day 8 Cairns. Sightseeing in and around. Overnight Cairns.
Day 9. Flying Cairns to Adelaide. Overnight Adelaide.
Day 10. Kangaroo Island. Travelling to KI and sightseeing. Overnight Kangaroo Island.
Day 11. Kangaroo Island. Sightseeing. Return to Adelide. Overnight Adelaide.
Day 12. Travelling Adelaide to Mt Gambier. Overnight Mt Gambier.
Day 13. Travelling Mt Gambier to Warrnambool. Overnight Warrnambool.
Day 14. Travelling Warrnambool to Geelong. Overnight Geelong.
Day 15. Drive into Melbourne from Geelong early. Offload rental car. Spend the day sightseeing in Melbourne city. Overnight Melbourne.
Day 16. Out to Tullamarine and get on a plane back to the States.
It looks pretty hard to squeeze that into 14 days.

Travelling from Adelaide to Melbourne via the Great Ocean Road is a long slow trip. There are many worthy stops along the way. We typically spend 3 to 4 days in each of the Mt Gambier area, Portland area, Warrnambool area, Port Campbell area, Lorne area. You will just have to push along and be selective about what sights to see.
Cheers.

@ Rfolkening.

Besides these world class natural static, flora, fauna, and oceanic attractions there are also the people who live here. Some with roots going back 40,000 years.

We have a national anthem that most recognise from the repetitive playing at international swimming meets.

But there is one song close to our hearts that tells the true story about us.

https://www.youtube.com/watch?v=rjkrjYitgeA

Makes even the toughest blokes tear up.

And when overseas on holiday or working, this one acts like a magnet to draw us home.

https://www.bing.com/videos/riverview/relatedvideo?q=Qantas%20Advert&mid=328922518E77EE516B7B328922518E77EE516B7B&ajaxhist=0

Chances are you will meet many like these.

In my humble opinion, anything you do in Aussie ( as we NZers affectionately call it ) will be great. But your itinerary does feel rushed. I would choose just 3 spots- all different, feels like several different nations within one country but I must say of all the countries I have visited in Asia and Europe, Uluru remains the single most amazing sight. I doubt I could ever see another natural form to eclipse it. I liked Adelaide but would award more time to Sydney and Melbourne TBH and may be skip Cairns. Driving distances are vast and can be tiring and you need some 'lolling' about time to enjoy Aussie spirit and camaraderie- there's lots of it! And personally, I really love Brisbane!

You didn't mention but don't forget the travel time "lost" coming and going from the US. Is that included in your two week window? On your flight, what class are you flying? Keep in mind you will be tired on arrival and adjusting the day after. Flying PE or BC may help somewhat, but expect to be tired.

Saying that, and as others have mentioned, Australia is huge. I don't like wasting time being in airports and planes while trying to explore a country with limited time. I would tend to explore the Sydney-Blue Mountains area and maybe just pick one other area. Any chance of extending the trip to three weeks? That could make traveling around a bit less hectic, especially for your wife.

I will take the opposing view about the Blue Mountains; I would definitely stay one night there. I don't know if you are hikers or not, but there are some nice hikes you can do along the rim, and it gives you a much different perspective than just being at the big parking lot where the bus will take you. I had a quick trip to Australia last year, and for me the Blue Mountains were much more interesting than Cairns and going out to the reef.

No argument from me re overnighting in the Blue Mountains. I last stayed in Sydney itself back in 1983 prior to the Sydney Marathon. Since then I have always headed straight to either Katoomba or Blackheath to stay. I might squeeze in a few hours of Sydney sightseeing if I have a later flight.
But old mate the OP has chosen a plan to visit a huge chunk of the eastern part of our continent. To do what he wants to do a few days of glorious hiking in the Blue Mountains just won't fit.
If I was recommending where to go and what to see and do to someone with the same likes and interests as me it would be very different.