Noel, you may be able to find descendants through the telephone listings.
http://www.whitepages.com.au/#Use the "Residential" tab.
If you put in the surname
Rea and
Warrnambool region you will come up with quite a few listings with that surname. Use Googlemap and you can see that Warrnambool is the nearest (14k) largish town to Yarptuk where the property was, and there are others in the same region
Who knows whether they will be your family but maybe worth a letter? There are no descendants of my own families who were in country Victoria now - all moved to the city.
Now - the beneficiaries of Margaret REA's will were Margaret DUNNE and Catherine KERR.
Margaret DUNNE, whose death certificate you already have.
PROV has a will for Margaret DUNNE but unfortunately not digitised; death date given as 14 January 1941, resident Koroit.
Whitepages has 2 listings in the Koroit area for DUNNE, however it seems to have been a big family in the area in the past.
Catherine KERR is not identified by relationship in Margaret REA's will so unsure of how to look for her.
Cando suggested that the Port Fairy historical society. There is also a Family History group in Warrnambool.
http://www.aigs.org.au/warrnamb.htmPerhaps if you list all of Margaret's children and their ages at the time of her death we may be able to get a bit further. I cannot see a suitable death for 60year-old James although someone else may have already posted it - too many James DUNNEs
Judith