I'm a member of Clan Donald - Glengarry as well. Cadet families are branches of Macdonald lineage, often the younger sons of a senior line such as Glengarry would obtain their own wadsets (leases) and the families decended from them would be known by the name of the property. Due to the heraldry conventions at the time, most cadet lines required a male descendant for the title to pass down. Examples of Cadet names are Lundie, Ardnamurchan, Leek, Greenfield, Scotus, Ardnabie, Sandaig, Shian ... there are about 115 cadet lines, many of which 'died out'. With immigration possibly some families thought to have died out have descendants in Canada that can prove their genealogical connection.
As to spellings, I totally understand. I have to check at least 4 variations when working with Mc/Macdonalds/ells.
My suggestion is to provide any specifics you can on the original Glengarry settling ancestor, lot # or nickname, military service, vitals and spousal info ...
There is a story now unfolding about a group that tried to immigrate to NY to join family that had earlier arrived on the Pearl, on a ship called the Glasgow Packet, but the ship was boarded by British Recruiters and the males were basically impressed into the BRitish Army, their families being shipped to Nova Scotia (or PEI) for the duration. Some people on the Macdonald in 1786 were returning to North America after their experience with the American Revolution. Many were captured (ie. Moore's Creek) by the Americans and paroled in exchange returning to Scotland in most cases for the balance of the war. The other UEL's came directly into the counties in abt 1786, although some are said to have arrived earlier.
Evelyn Goulet, Castle Tioram
Clan Donald International