GeneJeanie,
The marriage records for Moville RC are on-line on the rootsireland site. Unfortunately I don?t see this marriage listed. Moville RC marriages for 1857 have also been transcribed on this site, but unfortunately this marriage is not listed in them:
http://www.movillerecords.com/marriages1857.html
Patrick?s birth certificate in 1861 in Scotland should record the date and place of the parents marriage. Likewise the 1861 Scottish census should tell you whether Mgt junior was born in Scotland or Ireland.
The family appear to have been in Bridgeton, Glasgow in 1861, and there?s also a Patrick Cairney birth there in 1861 (GROS 644/03 0307). You can view the census and the birth records on Scotlandspeople (pay to view).
http://www.scotlandspeople.gov.uk
If you are sure that the family came from Moville, it might be worth checking the parish records, and searching a few years either side of 1857. There?s a copy on microfilm in the National Library in Dublin, and another in PRONI (the public record office) in Belfast. (It?s always possible that the spelling of the surname changed slightly with the move from Ireland to Scotland. Eg it may have been Kearney in Ireland. That sort of change was very common and could account for a failure to find the records in Ireland).
Unfortunately Moville RC baptism and marriage records only start in 1847 so you are not going to be able to trace John Cairney?s own birth through those records.
You should be able to get Margaret Donnelly's parents names from her Scottish death certificate. (Again look on Scotlandspeople)..
Elwyn