The 1841 Census (transcription at
https://www.freecen.org.uk/cgi/search.pl) has several M(a)cGugan families at Arinafadmor, North Knapdale
Angus McGugan 60 Farmer
Flora McGugan 67
Archibald McGugan 22
Euphemia McGugan 14 (SP indexes this family as MacGugan)
This information ties in with the information from the 1851 census already found by
runningbear. However I note that Angus MacGugan and Flora MacGugan had at least four children: Mary, 1806; unnamed, 1814; John, 1816; Archibald, 1818. Flora McGugan, widow of Angus (illegible but not McGugan!), labourer, died at Arinafadmore on 25 June 1866 aged 90, parents William McGugan and Mary McGugan, maiden surname McGugan, informant Euphemia McGugan, daughter. So Angus is not a misreading or mistranscription of Archibald, and this Flora is not Flora MacLean. Angus McGugan, farmer, 83, died at Arinafadmore on 7 February 1859, parents Donald McGugan, farmer, and Catherine McGugan, maiden surname McMillan. Informant Archibald McGugan, son.
Angus MacGugan 67 Weaver
Angus McGugan 14
No ideas who these are!
Archd McGugan 40 Weaver
Jane McGugan 35
John McGugan 11
James McGugan 4
Angus McGugan 6
This looks like the family of Archibald McGugan and Jane Campbell: John, 1829; Angus, 1835; James, 1837; Sarah, 1841; Archibald, 1843; Hector, 1845. I think Jane must have died, and Archibald married Ann Campbell and had Hugh, 1848, Duncan, 1850; Donald, 1852; Ann, 1854, and John 1859. The family is still at Arinafadmore in 1861
Archibald McGugan 55 Worsted weaver
Ann McGugan wife 40
Duncan McGugan son 16
Hector McGugan son 15
Dugald McGugan son 8
Ann McGugan daughter 6
John McGugan son 1
Catherine Campbell mother-in-law
There's also a MacLean family at Arinafadmore who might be worth a look in case they are related to Flora MacLean
Niel MacLean 40 Ag Lab
Mary MacLean 30
Donald MacLean 12
Niel MacLean 10
Dugd MacLean 4
Duncan MacLean 1
Arinafad More is on the shore of Caol Scotnish, north-east of Tayvallich. See
http://maps.nls.uk/geo/explore/#zoom=16&lat=56.0391&lon=-5.5995&layers=5&b=1On modern maps it is named as Scotnish, while the place called Scotnish on the old map is now marked as Scotnish F(ar)m. See
http://www.geograph.org.uk/gridref/NR7588Not far away, at Glaichintobair, is another McGugan family
Archibald McGugan 60 Ag lab
Catherine McGugan 50
Flora McGugan 12
Sarah McGugan 10
Ann McGugan 8
Catherine McGugan 3
Angus McGugan 6
This is the family of Archibald McGugan and Catherine McPhail: Flora, 1828; Sarah, 1829; Angus, 1833; Nancy, 1834. Archibald and Catherine were married in 1827. If Archibald's age is correctly listed, he would have been born between 8 June 1776 and 7 June 1781, so 1827 is quite late for a first marriage. Could this possibly be Flora MacLean's widower's second marriage? Noting that Archibald and Flora named their first son Donald, this may well have been the case. He died at Carsaig on 12 December 1864, aged 77, parents Donald McGugan and Catherine McMillan. So he was Angus' brother. His widow registered the death, but the certificate does not mention any other wife.
Anyway, to save rambling on, there are no other possible deaths for either Archibald McGugan or Flora MacLean after 1855. So (unless they emigrated, which seems unlikely if their son John was married in Scotland in 1854) Flora died after the birth of Malcolm in 1826 and before the 1841 census, and Archibald may have remarried in 1827 and died in 1864, or he may also have died before 1841.
I can think of several more possible lines of enquiry, but my brain feels like mush and I need a coffee!
Does that help?