If you look at the NSW birth indexes, for children with parents Edward and Violet, a number of possibles come up:
http://www.bdm.nsw.gov.au/cgi-bin/Index/IndexingOrder.cgi/search?event=birthsThere are also deaths for three of the boys listed.
In West Maitland there are marriages for some of the children and also what looks like a remarriage for Violet in 1920 to John H T Thompson.
The death index entry for: Violet Emily M. Thompson, d. 1947 Newtown, mother "Amelia", may be Violet Emily Maud's death.
One of her sons, Edward Alfred Mellon, may have signed up for WWI, lying about his age (he was b. 1900, signed up in 1918 and gave his name as Harry Gimbert, was discharged after a few months when they discovered he was under-age). He appears to have claimed that both parents were deceased! (as Harry Gimbert), but other letters mention that some money was paid to his mother.