I'm not sure about the pronunciation of Gauch (Gaich, Geach). Threestones is the man to answer that since his people are still in the Cabrach.
Your grandfather James Gordon was the illegit son of James Gordon, an ag. lab at Greenlone, and Isabella McDonald domestic servant. I don't know which James Gordon was the father, but his signature does appear on the birth certificate.
5 yr-old James appears in the 1901 census at Gauch with his maternal grandmother Beatrix (more commonly Elizabeth) Gordon. Her daughter Isabella McDonald (b 18 May 1869 at Gauch) was one of 2 illegitimate children she had with a John McDonald who was resident at Largue in 1856 when the first child James was born.
Elizabeth Gordon (10 Mar 1835 - 21 Jan 1918) was one of 3 children born at Gauch to Alexander Gordon & Elizabeth McDonald (married 1832 in Cabrach). She died at Largue.
Elizabeth McDonald born 6th Jul 1799 at Cromdale, Moray, died 31st Mar 1890 at Gauch.
Alexander Gordon b 8th Jul 1786 at Gauch, died 2nd Jul 1878 at Gauch. One of 10 children to John Gordon (died 27 Jul 1813 age 70) & Isobel Scott (died 1818 age 71). Most of their children were born at Gauch, but the first, in 1765 was at Alduny, which is probably where Isobel Scott was born. She was a daughter of Alexander Scott and Anna Henry, and Alexander was the son of John Scott the 7x gt-grandfather of "Threestones". You are probably also directly related to me, since I have Scott and Henry ancestors in Cabrach.
All the placenames mentioned apart from Greenlone are in Upper Cabrach, traditionally the Aberdeenshire part of the parish.