From another thread .....
.... pop up to Cooktown then nip across to Normanton ....
An almost 3000km pop and nip, probably more after getting lost and back tracking, in either case ....

.... Cooktown .... Cloncurry, Longreach ....
Having returned from our half-lap (mid-July to mid-October) towing the airconditioned caravan, staying in caravan parks (with pools) in unseasonally very hot (high 30's & low 40's) Winter & Spring, I hope that staying in hotels, motels and / or cabins is in at least some of the planning.
We didn't get to Cooktown or Normanton, so I can't comment on either of those places. We toured around and stayed in the Cloncurry, Julia Creek, Winton, Quamby, Longreach, Barcaldine area for two weeks, they're all little, lovely, (mostly) old, quaint, places. Plenty of old Queenslander pubs - finding accommodation shouldn't be difficult.
Julia Creek wasn't on the list, but it is a gem, the caravan park (I suppose they have cabins) an easy walk to town (good pub meal and good bakery - most forms of emergency services personnel were there each morning). Although the CP didn't have a pool, our daily rate provided a free Council pool (next door) ticket. I presume the locals are quite use to 70 yo's making fools of themselves in the artesian heated water park, and slides - we had fun cooling off.
Truck museum at Winton, QANTAS museum and Stockmen's Hall of Fame at Longreach are also worthwhile.
I was disappointed with Townsville and Cairns, just big effing cities these days - busy, crowded, traffic jams, no character, at least not the same as it was in 1975 (my last visit that far north was in '75, I suppose 49 years have got a lot to answer for).
Port Douglas had also changed, and whilst it had grown by a factor of about 10, and despite all of the trendy shops and resorts, it was a lovely place, hope you can put it on your list, it ain't far out of the way. A detour just to get a Mocka's pie would make it all worthwhile.