As others have said a request on find a grave may result in someone local being able to help with a photo - if a stone exists.
This page has a contact link to enquire about graves in Ford and Yew Tree (the two main RC cemeteries)
https://www.sarsfieldmemorialsliverpool.co.uk/memorials-for-liverpools-catholic-cemeteries/Though they may or may not be able to tell you if a stone exists, hopefully they will at least be able to give you an email address for whoever it is within the Diocese who would have that info.
I did find death notices in the old newspapers for both Edward and Sarah (not found one for Catherine)
Liverpool Echo March 7th 1921, page 8 col 8HEANEY - March 4 at 63 Langtry-road, aged 35 years, EDWARD, dearly-beloved husband of Sarah Heaney also dearly-beloved son of Robert and Margaret Heaney, 65 Thomaston-street. R.I.P.
Interment at Ford Cemetery, tomorrow (Tuesday) at 3p.m., Friends please accept this- the only intimation.
Liverpool Echo 21 April 1932 page 7 col 7HEANEY - April 19 at Walton Hospital, SARAH, widow of the late Edward Heaney. R.I.P.
Cortege leaves 14 Brock Street, for interment at Ford Cemetery, tomorrow( Friday) at 1p.m.
HEANEY - April 19 at Walton Hospital, aged 46 years, SARAH, beloved daughter of the late John and Catherine Mulcare. R.I.P. Sadly missed by Brothers and Sisters.
Boo