Hi John
A big Christmas welcome to RootsChat

As always with these things, verification of someone's parents, in this case from John Ferguson's death certificate, is important to be 100% sure that you have the correct parents.
Supporting your theory however is the 1851 Census entry for John and Ann:
John Ferguson 37, Gamekeeper, b. Clyne, Sutherland
Anne Ferguson 31,`b. Clyne, Sutherland
Hugh Ferguson 8, b. Lairg, Sutherland
George Ferguson 6, b. Lairg, Sutherland
Margaret Ferguson 4, b. Lairg, Sutherland
Elizabeth Ferguson 2, b. Lairg, Sutherland
Neil Ferguson 1 Month, b. Lairg, Sutherland
Elisabeth Mathesen 20, house servant, b. Dornoch, Sutherland
Hugh Sutherland 65, visitor, blacksmith, b. Clque (?), Sutherland
Certainly, if they followed Scottish naming paterns, you would expect Ann McLeod's parents to be called George and Elizabeth perhaps. Again, if you have a look at Ann's death cert., this would confirm her parents' names.
Regards.
Monica