Sandra,
I had a quick look on;
https://westernisles.wordpress.com/genealogy/Using Ctrl + f & type in Guernsey
This will take you back to your discussion & a reference by Angus (sadly now deceased & missed too)! which mentions the husbands of Hugh's sisters being on Guernsey etc. as you will recall but...
Is it possible your Hugh was also involved in the Channel Islands affairs even at later dates in some way like the brothers-in-law?
Have you found references to the brothers-in-law & their connection with Guernsey (other than what Angus wrote) as you may find ref. to Hugh there or elsewhere on the Channel Islands etc?
Your MacDonalds are so complex for me to follow (harder when it's not your own ancestors to relate to the same) but I'm wondering if using the 2 daughters forenames Charlotte & Amelia (not Uist names) without surnames may bring up anything on the Channel Islands?
It may be worth looking into where the names Charlotte & Amelia may have originated from another of your enquiries;
https://westernisles.wordpress.com/uist/Use the Ctrl + f & Amelia
Please note (in case you forgot) the links are under different headings.
Annie