For example I’ve considered spending 5 nights in Melbourne and surrounds, fly to Cairns for 6 nights in Cairns/Port Douglas/Cape Trib and then 2 nights in Sydney then fly back to New York.

That's not bad for August, but Melbourne can be pretty chilly in winter. I would probably lean towards three nights Melbourne and four nights Sydney - might be a better balance.

Rent a local car for Cairns | Port Douglas (where we much prefer to stay BTW), but you don't need to drive in Melbourne or Sydney.

Book those 2-3 domestic flights about three months ahead ... JetStar and Tiger are the budget airlines (although watch your luggage limits) - but they are both perfectly okay. Qantas and Virgin are full service - but they also have good specials quite regularly.

For domestic and international flights see:

• www.iwantthatflight.com.au
• www.webjet.com.au
• www.flightcentre.com.au

Airbnb is extensive in Australia, and also see www.wotif.com.au.

I wouldn't be concerned about "less touristy" in Australia ... the prime tourist destinations are few and far between, but they are very good when you get there. Port Douglas will be nicely busy - Melbourne and Sydney will be just half-busy in August.

Do a long day-trip by bus for the Great Ocean Road (GOR) out of Melbourne - you can buy half-price tickets at Half-Tix at Melbourne Town Hall. But with five of you, I would rent a car for two days, and overnight at Apollo Bay.

Somehow I managed to buy tickets :) But girl I met spent around 12-14 hours in bus to make this trip.

So you are flying into La Paz at the start of this 10 week trip? You can fly to Sucre, then bus to Potosi and if you have time bus to Tupiza and take the 4 day jeep tour to Uyuni which is what we did and is spectacular. Being in Sucre will help with acclimatizing but you should consider taking Diamox as well. From Uyuni you can fly to La Paz or take an overnight bus. If you don't go to Tupiza you can get to Uyuni from Sucre via Potosi by bus. La Paz deserves a few days. So then instead of flying to Cusco I assume you would like to see Lake Titicaca so take a bus to Copacabana and go to Isla del Sol. Then from Copacabana to Cusco you can take an overnight bus (10 hours or so). You need (at least) 2 weeks for Bolivia with Tupiza.

Then you will want 5 days in the Cusco area for Cusco, Sacred Valley and Machu Picchu. Then fly to Lima. If you have time go to Arequipa (flight or overnight bus from Cusco) and the Colca Canyon, overnight bus to Ica for Huacachina, then Paracas and Lima. If you don't have time for that you can take an overnight trip by bus from Lima to Huacachina but I would not skip Paracas (Ballestas Islands and Paracas Reserve) because I liked it better than Huacachina and I would actually suggest skipping Huacachina so you can visit northern Peru after a day or two in Lima. You can take an overnight bus or fly to Trujillo (Chan Chan and Huaca de la Luna), bus to Cajamarca, scenic bus ride to Chachapoyas (Kuelap!, Gocta Falls...), overnight bus to Chiclayo/Lambayeque for the Lord of Sipan museum. If you fly to Piura you would miss all that. I have not been to Piura or Mancora but I would prefer visiting the sites I just mentioned to going to the beach. You will want at least two weeks for Cusco to Chiclayo (that is without Arequipa, Huacachina and Paracas... add a week). I have not been to Ecuador but again, I find your itinerary a bit odd as you will miss Cuenca and Banos and the whole inland route to Quito. And if you do go to Montanita there are direct flights to Quito.

Then in Colombia, instead of flying to Cali, visit San Agustin, Popayan and Tierradentro! It would be on the way and it would be a real shame to miss those places. You have so many flights planned... Don't fly from Cali to Medellin either. Go via Armenia to Salento and the Cocora Valley. Then via Pereira and Riosucio to Jardin and then to Medellin. Or at least visit Guatape as a day trip from Medellin and Jardin as an overnight trip. Otherwise you only see large cities and not the colonial towns Colombia is known for. You need 3 weeks in Colombia for what I suggested.

So I think you have time for most of my suggestions and you can even add Arequipa and Colca in Peru. And you don't need 4 days in Cali or Cartagena or even Bogota.

When I said 5 days in the Cusco area I meant without a trek. Add a few days if you want to do a trek instead of taking the train to Aguas Calientes for MP. The Inca Trail is sold out for September but there are other treks you can do (Salkantay, Lares...) when you get to Cusco. If you want to hike a mountain within MP (Huayna Picchu or Montana) you should buy MP tickets in advance as well. Check availability (and buy tickets) here: https://www.machupicchu.gob.pe/inicio

I would take less flights and with the ones you really need wait till closer to the date so you have more flexibility.

If you hire a car, it'll make the trip to TDP more quicker from Puerto Natales (if you manage to get a flight there). No need to wait around for a bus. If you fly straight down you may have 2-3 days in the park.

Would I do the W trek in that time, probably not.

I'd grab a car and do plenty of day hikes (Mirador Cuernos, Mirador Las Torres etc). There is plenty to see within the park if you are willing to drive and do some hiking.

Hey!
The weather in July and August is mostly clear. But in high altitudes, it's frequently changeable. So to accurately plan your trip to avoid strong pourings arrive in KG in time between new moons phases. Because usually when the new moon comes it's pouring with all components(Strong wind, thunders, etc).

The road from Arusha to Dar es salaam is all Tarmac. Take the Dar Express bus from Arusha to Dar es salaam and you will enjoy the country. One or 2 days tour in Dar es salaam City is worth the while. Don't go to Zanzibar without booking if you are on budget, you will be switched on to very expensive accommodation being told that the cheap ones are fully booked. Our friends went there without booking and were trapped by that situation. We are going there during December but we will book in advance.

..... how long will you be in Morocco for, where do you arrive and depart, can you depart a different port, might facilitate a better trip and avoid backtracking.?

As mentioned above, a good guide book, something like the trusty LP should help you make choices and peak interested in stuff you might be interested in, these pages are best to refine itineraries you come-up with.

Keep in mind the Railway Network in Morocco, ONCF a combined Train and Bus company, and the intercity coaches, there's also an intercity public shared grand taxi system, so hiring a tour company isn't necessary.

http://www.oncf.ma/
http://www.ctm.ma/
http://reversehomesickness.com/africa/taxi-fares-morocco/