Just to clarify the location - is this your Christopher & Margaret on the 1911 census ?
The household is resident in a townland named ‘Rock’ in Santry civil parish County Dublin - Drumcondra is the Electoral District. There’s a seperate location, a civil parish, named Drumcondra or Drumcondrath in County Meath.
The McGuiness household at Rock townland consists of Christopher a general labourer age 60, his wife Margaret age 55, two sons Christopher jnr. age 21 and Michael age 19, ‘Grand Niece' Julia age 15 and a boarder named Christopher Farell. All in the household are Roman Catholic and born County Dublin, the census form was filled by Chistopher.
Chistopher and Margaret report that they are married 26 years (c1885) and had four children, two of which are still alive.
I located a possible birth for Chirstopher (jnr) with parents Christoper McGuinness and a Margaret Taffe which I’m checking into… their residence is Corballis, which the name of a townland very close to Rock townland - both of these are close to where Dublin Airport (formerly Collinstown) is located now… I’ll check further into this line and update here tomorrow..