Just found this site and all these informative posts! I am also interested in the Dan McDonald connection in Cape Breton.
I have some info related to this family, the John McDonald who came to lot 59.
From his family bible --
John McDonald was married to Catherine McInnis by Rev. Alex Munro of Valleyfield, PE.
They had eight children and raised them on the farm that would be designated as one of the Century Farms in PEI. (Farmed by the same family for 100 years -1867-1967)
Their family: Norman born June 9, 1861, Angus Martin born June 5, 1863, Neil born July 21, 1865
James born Feb 24, 1867, Daniel L born March 19, 1869, Jessie Margaret born April 14, 1871 (died March 3, 1864)
Elizabeth Catherine born May 4, 1873, and another daughter also named Jessie Margaret born March 15, 1875.
Norman had a first cousin affectionately called "Cousin Alex". He lived in Cape Breton and made regular visits to his family in PEI. He was a minister.