Aren’t there photos of at least one aircraft (to my inexpert eye it looks like an Islander? - high wing, twin engined thingy -) on the Lake next to the Bluebird?
I would say at a guess the aircraft is the Aerocommander 500 that Campbell's missus used to fly. I remember seeing it back in the days when he was doing his thing on Lake Bonney in Barmera.
DF.