This is a proud ad for WA.
Gday Marty. I have traveled most of Australia, no disrespect but Adelaide/ Darwin via Alice is best done on a train where you are sleeping for at least 50% of the time.
Taking that route you are going to miss the best part of Australia & also the largest by far " WA". The Southwest is absolutely unique in flora, with the largest trees in the southern hemisphere. After the Nullabor, Esperance is a great stopover & there are fantastic new facilities at the Cape Le Grand site which is run by volunteers for the Dept Conservation. The Hopetoun National Park is a great area to visit on your way to Bremer Bay. Continue to Albany & dont miss Mt Clarence & the views from the memorial. Denmark is worth a stop over on the way to Walpole & the valley of the giants. Denmark has an active aviation club & a unique airfield on the top of a hill.
The drive through Karri forest to Manjimup is a high light to any holiday. Manjimup also has an active aero club where you may get a flight if your lucky. Not to be missed is the fire lookout on the top of a giant Karri tree South of Manjimup. Free to climb if your fit & game.
Drive from Manjimup to Bussleton vis Donny brook & see the fruit orchards. Bussleton has the incredible mile long jetty with a rail line & under water sea aquarium. If your not into walking take the tourist train. A little South is Yalingup with probably the best surf in Australia. The Caves are also a must see, with guided tours every hour. There are a number of amazing limestone caves in the area between Yalingup & Augusta.
Drive to Perth is an easy 2 hours from there.
Perth! the Swan river, got to be the best location of any City in the world. Lousy architecture with virtually no history. Kings Park makes up for that with stunning views across the Swan River. The beaches in WA are the cleanest & best & they stretch for over 10,000 Km . Heading North Lancelin is a must for the fishing & FWD tracks over the dunes & if your game through to Jurian Bay on dirt roads & beaches. Sample the Rock Lobsters at Lancelin, in good supply due to loss of sales to China.
Geralton is a good stop over, after there is a long drive North, but Shark bay is a must see. If you have the time the western most point of mainland Australia is Steep point. Managed by CALM & has amazing fishing. It is possible to catch Spanish Mackeral from the rocks off Steep Poit. Note FWD only. The view to Dirk Hartog across the North West passage from there is amazing. ( UNESCO's official listing of Shark Bay as a World Heritage Site see Wikipedia)
Next stop Carnarvon a lovely coastal town, famed for bananas & fishing.
Ex mouth is worth a visit, you can get to swim with the whale sharks at Ningaloo if your there at the right time of year.
Then through the mining towns, Dampier if you want to go game fishing. See the salt mines (lakes) the mountain of salt at Karatha. A short drive to Roeburme which was the main town in the North west in early days, better travel through & visit Cossack which has interesting old buildings & excellent fishing.
Broome is a good stop over on the long journey North to Darwin. Treat your Mrs to a pearl neck & visit the pearl farms & try the oysters.
Head North & stop at Halls Creek & say hello to the guy who looks after the airport, Take a flight over the Bungle Bungles. Next must see is Lake Argyle great camping & a good place to rest for a few days, before the drive to Darwin.
Give me a call if you get to Perth,I will be able to take you for a flight & show you that SABC has the best grass runway in Australia. See <https://www.sabc.org.au>
Good luck in your travels.
John