Australian National Archives Service records - Arthur john's has been digitised so you can read. It says he died in 2/03/1950 and has his Widow living in NSW. They originally settled in Western Australia but Arthur and Hilda moved to NSW but son stayed in Western Australia. So WA would be a good place to seek out descendents.
ENNIS ARTHUR JOHN : Date of birth - 07 Feb 1893 : Place of birth - COUNTY DOWN IRELAND : Place of enlistment - FREMANTLE : Next of Kin - ENNIS HILDA
Access status: Open Location: Canberra 1939 - 1948
1939 - 1948 5590448
B884 W29456 ENNIS ARTHUR GRANVILLE : Service Number - W29456 : Date of birth - 08 Jun 1919 : Place of birth - STOKE ON TRENT ENGLAND : Place of enlistment - PERTH WA : Next of Kin - ENNIS A
Australia Death Index, 1787-1985
Arthur Granville ENNIS died 1978 Perth WA
New South Wales Death Reg #:3507/1950 ENNIS ARTHUR JOHN Father: ROBERT District: CONCORD