RootsChat.Com

going on the theory that Harriet Goodman was infact the grandmother in 1901 rather than just a boarder I found a civil record that fits with your date of marriage
Dublin North Oct-Dec 1880 V2 P491 Anne GOODMAN with a match for John MURRAY
If this is correct and the fact that Harriet is not listed anywhere in 1911 this death record may be her
Rathdrum Jan-Mar 1902 aged 64 V2 P777
This record if proven correct could give an address and therefore a pointer to where she is buried
Also if this is William
Dublin North Jul-Sep 1902 aged 16 V2 P361
then he may have been buried with his grandmother as their deaths were so close

The birth record for Michael you have probably seen in 1920
Dublin South Apr-Jun V2 P592

You can order certs from the General Register Office in Roscommon and request a search

From a logical point of view there are birth records for a Mary Esther in 1925 and two John's in 1926 (also a death for John) which you could follow up on

Barntap
Do not rule out Mount Jerome I found catholic relatives buried there in both private and common graves buried before 1922
It was not common but was possible

Had a quick look to see if i could help

I found these civil records that may be John and his family if the Mountjoy
link is correct for names

Marriage William JOHNSON to Margaret JOHNSON Rathdrum Oct-Dec 1882 2/807
Birth William JOHNSON Rathdrum Jan-Mar 1884 2/916
Birth John JOHNSON Rathdrum Oct-Dec 1887 2/816
There are deaths in Rathdown that could be William in the 1890s making Margaret a widow in 1901

There is a marriage for William JOHNSON Jul-Sep 1919 Dublin North 2/488 which maybe John's brother particularly in light of the obituary

There is a death record for Mary Esther Johnson which maybe John's first wife in Dublin North Jan-Mar 1918 aged 23 2/374
and a birth record that maybe Evelyn as Evelyn Maud Dublin South Oct-Dec 1913

The second marriage is easier to follow as it is later and by entering COADY as the mother's name you can see three entries for children on www.familysearch.org (not giving details as maybe living people)

These may or may  not be correct but they could be a good starting point