Deaths of Robert and Elizabeth:
1923
MEAD, Robert
Male
Perth
#1012
MEAD — On August 27, 1923, at the Perth Hospital, Robert Mead, late of Jarrahdale, the beloved husband of Elizabeth Mead, oldest son of the late Henry Mead, of Beenup, and fond father of Mrs. W. Miller, Mrs. R. Tonkin, Mrs. C. Facey. and Messrs. George, Henry, James, and Walter Mead, aged 78 years.
http://trove.nla.gov.au/ndp/del/article/226202691934
MEAD, Elizabeth
Female
Jarrahdale
#9
MEAD - On August 6, at Jarrahdale, Mrs. Robert Mead, widow of the late Robert Mead, loving mother of Eliza (Mrs. Tonkin), Annie (Mrs. W. Millar), W. G. Mead, Harry, Jim, A. W. Mead, and Emiline (Mrs. Pace); aged 83 years.
http://trove.nla.gov.au/ndp/del/article/32953749It seems you have the wrong family for Frederick.
You may have seen these articles:
http://trove.nla.gov.au/ndp/del/article/83700061http://trove.nla.gov.au/ndp/del/article/32403189 (I think his age here should be 55, not 75)
His attestation papers - he was discharged after 3 months.
http://soda.naa.gov.au/record/8006466/7Debra