I think the townlands the two families come from are Oughtmeen and Leckbeg. Both are in the RC parish of Lettermacaward.Unfortunately it has no baptism or marriage records prior to 1876. Civil records start in 1864 but again that won’t help in this case.
Griffiths Valuation lists Bryan McCarron in Oughtmeen in 1857. He had a house and a share of some land on plot 2. That’s amile or two south of Dungloe.
Leckbeg is a few miles north of Dungloe and is near Burtonport. Griffiths lists a Hugh Boyle there with some land (plot 1) and John with a shop and 2 acres.
One McCaroon household in Oughtmeen in1901 who are presumably close relations of your family: