These are the two civil births I located for the sons shown on the 1911 census - both births show residence and place of birth as townland of Corballis, both are registered by their mother Margaret using her ‘mark’, and shown in the register as variants of McGuiness.
Christopher Maginnis born 1st June 1889 (entry 137 on the page - see the image link on the entry)
Michael Mcgennis born 15th February 1892 (entry 286 on the page)
I also located a transcript of the Catholic Parish record for Christopher Magennis and Margaret Taffe on RootsIreland - the marriage took place in Catholic Parish of Swords, County Dublin on the 25th January 1885, the town of Swords is about 5km north of Corballis and Rock townlands. Christopher’s residence is given as ‘The Boot’ and Margaret’s as Collinstown, their father are named as Andrew (McGuinness) and Michael (Taffe) - there were four witnesses to the marriage : Nannie Magennis, Juia Taffe, Patrick Cooke and Anna McCormack. I also found the corresponding civil marriage.. Christopher Maguinness & Margaret Taaffe 25th January 1885, some additional information is included in this it appears that Christopher is a widower, so not his first marriage both are 'full age' so age 21 or over, the groom's occupation is shown as labourer, his father is a farmer, Margaret's father is a labourer. The registrar has included some sort of note from the priest regarding refusal of the husband to hand over payment..
I’ve included a link to the entry for the townland of Rock below - if you zoom in on the map you can see the adjacent townlands of Corballis to the south-east and Collinstown to the south-west.
Placename Database - Rock Townland, Santry Civil parish, Couty Dublin
Tracing forward from 1911 can be difficult as people didn't always stay in the same area and privacy rules restrict records - i.e. civil births cut-off 100 years ago, marriages 75 and deaths 50. Most ordinary people left very few official records, but if Michael stayed and married in the same area, he should appear in the civil marriage records on IrishGenealogy - the registration district for this part of County Dublin is Balrothery, its a case of checking the individual marriages for clues to see if they match this family - e.g. father's name & occupation, residence of the groom. The deaths online cover up to 1969, so there may be a record for him online - these can be more difficult to confirm, as death certs dont include very much detail other than date place and cause of death, and name of the person who registered it - the informant.
The surname McGuinness has a number of variants as you seen, and in the 19th century was common across much of Ireland, most concentrated in north Leinster and South Ulster, but with clusters in other areas the midlands, Antrim/Derry, Sligo/Mayo etc, and present to some degree in many counties with the exception of counties Cork & Waterford. The surname Taaffe is less common and concentrated in counties Meath and Louth, with smaller numbers in Westmeath and other counties across Ireland.
I have not as yet been able to locate your McGuinness/Taaffe household on the 1901 census, will update here if I locate any further details..