If the 1911 census return is accurate then their marriage was in about 1861 - so before the start of civil registration for RC marriages, which means you would have to search for parish records for the marriage and their baptisms.
Their ages are a little inconsistent between the 1901 and 1911 census returns, so ages and years married could be a little bit inaccurate..
If the couple were married in Westport then the RC parish to check for is Aughaval - sometimes noted as Oughavall, or 'Aughaval, Westport & Lecanvey'. Marriage records for the parish go back to the early 1820s, baptisms go back to 1845.
Shane