Looking for information etc about family history circa about 1911 to 1936

My husband's mother was born in Ballylennon in about 1911 to 1914 her name was Elizabeth Dunne daughter of John Dunne and Mary Kelly, she move to England in about 1936 where she married John Shanahan. 

I have looked her up on the census of 1911 and it gives her age as 5 months none of which matches with her Birth Certificate 1914.I can only find one John Dunne in Ballylennon so presume it must be them but her brother and sisters all seem to be out of order and date plus there are morea than were ever mentioned by her as she passed away in 1976 information is now only half remembered from the rest of the family.

Any help etc would be very much apprieciated.