A Request for Research Help

I sent the following message to a genealogy contact in Ireland:
A cousin of mine is planning a third and final genealogy trip to Ireland this summer.

She has asked me for suggestions.

Firstly, what we know:

The family of Andrew and Jane Buchanan (last name probably McNeilands or Young) left Ireland in 1847 during the height of the great famine. At this time they were living in Binnawooda townland, near Drumquin. The children we know of were:
Robert, christened on 20 Apr 1815, Derg Parish Church, Castlederg, Tyrone, Ireland
Charles, christened on 26 May 1817, Derg Parish Church, Castlederg, Tyrone, Ireland
(Charles was already married to Ann Porter in Mar 1843 at Killeter Presbyterian Church, Termonamongan Parish, Tyrone, Ireland)
James, born about 1823, probaby Learmore townland, Tyrone, Ireland
William, christened 28 Mar 1824, Derg Parish Church, Castlederg, Tyrone, Ireland
(William was already married to Ann Thompson 24 Mar 1846, Lower Longfield Parish, Tyrone, Ireland)
Andrew, born Abt 1826, probaby Learmore townland, Tyrone, Ireland
John, born 10 Aug 1829 according to the 1901 Canada Census (he is inconsistent)
Samuel, born 28 Mar 1832 according to the 1901 Canada Census (he is inconsistent too)
Jane, born 27 Feb 1836, Omagh, Tyrone, Ireland according to her gravestone.

The ship ran into a severe storm and had to return for repairs. On the second attempt they arrived in Canada and were quarantined at Kingston, Ontario, where Andrew and his son William's baby daughter died of "immigrant fever", which was probably typhus. After the quarantine, the men found work harvesting, before they found an area to settle.

The family's history from that point is fairly well documented, as they settled in virgin wilderness that later became part of Elma township and Perth county, Ontario.

On her previous trip my cousin found a Buchanan who was willing to do a YDNA study that happened to be a perfect 67-point match for her brother's YDNA, an amazing accomplishment! Unfortunately, he doesn't know his ancestors any further back than we do. Some stories in this newly-discovered connection vaguely point to unidentified relatives in County Donegal, which would not be unreasonable geographically. But we have nothing tangible (names, dates, places).

Are there records or resources that you are aware of that might help us? We would love to find the marriage of Andrew and Jane or their ancestry. I realize that research in Ireland is a challenge, and we are probably very fortunate to have found these christenings and marriages. Any suggestions would be most appreciated.
 
 
Bill Buchanan