Thanks for your question! We get far too few messages here.
As to the Wilkinsons, they were not affiliated with the Gaelic Clann Dhòmhnuill, AKA the Clan MacDonald. As I stated in a response to another researcher of the Wilkinsons, the name is actually English/Lowland Scots and not Gaelic. This in unfortunately very confusing, as there are many websites and quasi-historical books which erroneously link the Wilkinsons to the Clan.
It is most interesting to me that you heard/read Wilkinsons were in Islay in the 1400s - the people of Islay would all have gone by Gaelic patronymic names like "Dougall Mhac Allan Mhic Iain" or "Mairi Ni Donall", and would not have had fixed surnames.
I hope I have been of assistance.