I may have responded to another of your posts. The names look familiar. Excuse me if this response is redundant.
I research the Irish Family History Foundation's database. It contains 12,800,000 surviving rcds for abt 70% of Irish counties. Rcds are increasingly sparse B4 1840, rare B4 1800. Cos. Donegal and Derry were recently added to the database.
Note 1 - Without a KNOWN county, the chance of an ancestor's rcds NOT being in this database is AT LEAST 30%.
Note 2 - Only 1/2 of Co. Cork's rcds are in this database.
Note 3 - The RC church kept control over most parish rcds from Tipperary (north). These are ONLY available thru the Tipperary Family History Research center at a substantial fee (regardless of outcome).
Note 4 - The National Library of Ireland (NLI) has microfilms of parish church rcds.
For El(len) Callaghan M 1871 +/- 4 yrs, Carndonagh CR, Co. Donegal, I found 3 rcds. One in 1871 is listed as an ELLIN.
For Dan(iel) McDaid M ditto, I found 1 rcd in 1871. These are likely for your ancestors. A view of the detailed rcds should show they married each other. If so, the view will likely reveal their parents' names as well as other info.
I didn't find earlier B rcds for either Ellin, or Daniel. This infers they were likely protestant. Protestant rcds are most conspicuous by their absence.
You should search for the forenamed children specifically in Carndonagh, and Co. Donegal in general.
Google the Foundation's name to lead you to this database. Register, opt to be notified as rcds are added and browse. Pls post your search results to my genforum msg.