If you look up the 1911 Irish Census you will find Sarah Cahill in No. 3 Henry St. Cork along with her siblings (11) also her Father Joseph and Mother Rosanna. 24 yrs married.
On Family Search she is married and I could only find 2 children William born Cork 1935 also Mary A born 1931.
If this is correct you should have no trouble finding William on the Census.The 1911 also will give occupation etc. If you have let me know