I actually used your webpages to find the links to the Drinagh and Drimoleague records. Armed with Michael and Ellen's names, I did an exhaustive search and came up with the marriage date you quoted as well as the set of kids. They are the ancestral couple that I suspect is mine.
Knowing the specific birth order of the four "Philadelphia McCarthy's" my exhaustive search traced back to that one couple. My mother (who is now 84) has vague recollections of her grandmother (who was the youngest, Margaret) speaking about some proximity to Skibbereen but the lady rarely spoke of the "old country." I did a similar search in the North of Cork (just to be thorough) - but that was a bust. As a result, I have a level of confidence that I have found the right family in Drimoleague. Adding to that, the four McCarthy sisters had a cousin, Hannah Crowley, that immigrated to Philadelphia and her manifest entry was fairly rich, citing her home in Dunmanway. This woman, cited parents on her marriage license named Michael Crowley and Mary McCarthy. So, I feel fairly confident that this general region of Cork is correct for "my" McCarthy family.
I had also done as you suggested and looked at the sponsors listed on the baptism records for all the listed McCarthy children, I noted the names of people with the same names (Driscoll and McCarthy). Going back over the Cork Birth/Marriage records, I made an assumption that the sponsors with similar names were likely siblings to either Michael McCarthy or Ellen Driscoll. A search of the records found one set of common parents for the named Driscoll “siblings;” namely, Daniel Driscoll and Anne Richardson (of ‘Drinah’), married in Drimoleague on 13 Feb 1831. - So your guess that Daniel may have been Ellen's Dad also agrees with what I think may be the correct set of maternal grandparents. I have not had the same degree of success with the McCarthy side to date.
Only one of the Philadelphia McCarthy women gave birth to boys - and one (her second) was James. Most of the girls born to the four share names with this larger Drimoleague family. (including two Anne's, Mary, Julia, Hannah, Nellie, and two Margaret's).
Thanks for your help. Any additional insight you may have is greatly appreciated.