Hi Suz,
The Sutherlands and the Mackays from Durness are sometimes difficult to unravel. Apart from trying to establish which Mary married the Roderick Sutherland born 09.09.1793, can you tell us who you are trying to trace?
A distant cousin, Angie Lamb, sent me some of the information she had found, and she has him marrying Mary Mackenzie, but she did not send a confirming reference.
I can tell you, though, that at least three you have shown as children of Roderick and Mary Mackay were, in fact, children of Mary Mackenzie. They are Kenneth (Nov 8, 1820); John (Oct 20, 1823); and Boyce MacKenzie Mar 26, 1826). Angie has shown all those you listed as children of Mary Mackenzie, and I can confirm that Jane/Jean and Angus are shown as siblings of Boyce in the 1851 census.
It is curious that in the Balnakeil Burial Ground, #67 records Kenneth Sutherland (Angie's family); #68 records Boyce Sutherland (again Angie's family) and #69 records Rory Sutherland (and Mary Mackay (the one you mentioned)
I suppose it is just possible that Mary Mackenzie and Mary Mackay are one and the same?
Not much help I'm afraid; but don't give up.
Ian