As for my interest, apart from a general one in piping as in Argyll I have both the MacFarlane and MacPhedran piping dynasties in my tree, my MacMillan roots are in the Uists. That, incidentally and despite the coincidence of names, makes an overlap with MairiD's quoted family just after 1800, very unlikely. The origins of my MacMillan family/name has nothing to do with the mainland and specifically Knapdale clan. When the priests had to come up with an Anglicisation of Gaelic surnames or patronymics, they simply borrowed known surnames from the mainland and applied them in the islands, in the case of MacMillan to any name that shared the Maol root.
Whilst part of the piper family may at some point have been located just north of Kilberry, Angus is always said to have been a couple of miles south of the castle at [sundry spellings] Lergnaheuisian. Angus himself was not present in 1911 but what would seem to have been his father was: Donald McMillan 78 farmer Lergnahuision, Kilberry, Catherine 72 wife, Duncan 28 son working on the farm. The next door record was for Neil McMillan 43 farmer Tiretigan, Kilberry. All are shown as born in Knapdale, which fits with the Uist connection always being described in the books as grandpaternal but raises a bit of a puzzle about John from Uist in the earlier message as his father on his 14.3.1900 death record is given as Donald. If his birth date calculated from the 1891 Census was about 1830, then he would presumably have been a brother of the Donald in the 1911 Census, born about 1833. This suggests that, rather than being imported as pipers at the end of the century, the family may have removed to Kintyre between 1830 and 1833.
Hope that makes sense. Best wishes Angus