Wysiwyg - I usually put way too much thought into stuff so I'd buy something to use and take it up with me to make sure it was the exact one that I wanted! I like to over think things too much!
Those Colman instant up tents are not canvas they see that rips stop stuff and have little vents at the bottom.
Not that your LOs don't need day naps you don't need to worry about it being hot in the day time inside the tent I guess so anything should be fine.
Jealous you get to go up there this year. I want to do Adels grove, Lorella springs, litchfield again. DH wants to drive the nullabor and get all the way to monkey Mia.
I tend to be the opposite and under think things a little mostly - I am trying to find more of a happy medium - although not an Aussie I seem to adopt the "She'll be right" mantra a little too much with some things :-)

I think looking at weights a canvas tent is out of the question if flying it to and from Darwin anyway - I need to go and check out a shop and see which I think offer best ventilation.

I think I have been to Adels Grove - it was lovely - we did a trip on the Desert Venturer from Darwin to Cairns in 2006 and I am sure we stayed there (just for one night unfortunately - but in their posh camping tents) and there was a really interesting talk that happened to be on about the Thylacine. We did a canoeing trip, and some swimming. (I remember the tour driver looked a bit like Hugh Jackman as Wolverine and lots of the girls on the trip were doing a lot of ogling and he just went swimming in his Levi's)