Now I see the problem! I'm reading too fast, and assuming too much. :-\
Since you're writing from Australia, and I never heard of Kildoorus (I'm sure I'm far from alone there), I assumed that was a town in Australia. After a bit of googling, I see we're talking about County Clare, Ireland.
Here are a couple of results from a quick (and slightly better informed) search:
1901 census of County Clare shows a farmer named Patrick McMahon. His age would put his birth year at about 1859. Immediately below him are wife Anne, 4 daughters and two sons.
FamilySearch.org has less promising results. There are a few records for men named Michael McMahon with sons named Patrick, but those Patricks were born 1864-65.
Good luck!