Nigel
We did a similar trip 3 years ago, like you after having been there many years earlier. I was so impressed that last year I spent a week bushwalking in the West Mac ranges and shortly will be off for another few days there. I'll be back home around 5 Sept so I can let you know what the mice are like, we plan to sleep out again, using a tent as a last resort!
For a good summary of that area and the various gorges, look up Mother Hens blog on their Central Oz trip, it. You should be able to search it.
Your trip should be comfortably "doable", with the odd long days.
Consider spending just 1 night
Coober Pedy and a night at
Arckaringa (spelling ?) Station at
the Painted Desert, it's only about 200km from CP. You can go further onto
Oodnadatta and
Dalhousie Springs, Finke, Lamberts Centre and avoid some duplication.
Your kids will enjoy the time back in civilsation at the Big4 in
Alice Springs, ours certainly did. But again consider one night less and stay a night at Ormiston Gorge NP
Camp site after Kings Canyon. As Mick said the Ormiston Gorge Pound walk is very good, will probably take 4 hours. For me it is superior to the better known
Simpsons Gap &
Stanley Chasm, yet only about 90 minutes from Alice
There is much to learn about Australia out there from the locals than just the "tourist attractions". Consider Kings Ck Station when you go to Kings Canyon for that reason.
Mark