Patrick Ryan Born in Edenderry

I am having difficulties tracing my grandfather Patrick Ryan Born 1877 in Edenderry, Kings Co. He married my grandmother Margret Connell in 1902/3. they lived in Dublin and had six children.Annie, Clare, Patrick, Michael, Benny, May. He worked as a gardener for the botanical gardens in Dublin and also as a foreman in a flour mill, I believe to be  Bollands.He may have spent some time in liverpool working for Vickers on shipbuilding. I have found them on the 1911 census, but not before or after, I know he died before 1951, but not much else. Wife margret died in april 1964.

I have found a Baptismal record for a  Patrick Ryan that was born  in Edenderry to parents John Ryan and Elizabeth Quin, but have nothing more  to prove this. 

I intend visiting Dublin in April and will try and research at the NLI etc. 

Can someone tell me why most of the geneology sites fail to find information about our ancestors, which we already know to be true, yet searchs constantly fail on those sites,it cant be good for business. 

I know that if I could be sure they were providing an honest and at least a fairly accurate search I would not resent paying. Rant over)- 

I would appreciate any help which might point out the errors of my way. 

Thanks in advance.