From what I gave you I would check out the family Lot and obtain an abstract. Contact as follows:
Land Registry Office
63 Kenyon St W, Alexandria Tel 613-525-1315 Fax 613-525-0509
Ask for an abstact on Lot 31 in the 5th of Kenyon and look for any document relating to your people like land grant, bill and sale, last will etc etc. Then order copies of all these docs for more detailed info.
Your Finlans were in St. Catherine's records as well as St. Finnan's so you should go there and try to obtain a birth or marriage record which will show parents names as well as maybe where they came from.
So far we show your Donald 1839-1916 son of John Finlan and Mary MacDermid (McDermot) and John's father as William and his mother as Margaret MacDonald. It may be that William was your first settler from Ireland.
There is only one mention of Ireland and it is for a Mrs. James Finlan from Wexford Ireland but not necessarily your Finlan's.
No point in going to Ireland until you have all your homework done here first.