I'll answer my own question in case somebody else is looking for the same thing. A distant relation sent me this email about Reg Doohan:
"One of my cousin's girls got stuck into the search for Bert's wife and son. The trail in W.A. was cold but eventually with help from Bev Doohan and myself she finally located part of the family in S.A. We knew that Bert's son, Reg, had married and moved to W.A. It now transpires that Reg died in W.A. aged 79 on 3rd May 1997. Folllowing his death his wife Betty moved back to S.A. where they had two married daughters. It was through one of the daughters that eventually phone contact was made with Betty who gave the info about Reg's death"