I would look for death first to establish dates, and then work from there (for those that died after 1864). If the family were reasonably well off they may have had a death notice placed in a newspaper, and knowing the date would help focus a search. A death notice may give the name of the church and cemetery used.
Very few RC parishes kept death/burial records, and if the cemetery used was a shared Church of Ireland one then it's unlikely that any RC burial would be noted in their registers.
There's a list of Dublin City & County graveyards on the Dublin City Library website - see : http://dublinheritage.ie/graveyards/