Hullo Corinne
I've had a look at the birhts in Applecross around the period you mention. There are an awful lot of John and Kenneth MacLennans.
http://freepages.genealogy.rootsweb.com ... #PageTitle
So you don't have an easy task, sorting them all out.
Unforuanately, many of the mariages (OPRs), before 1855 hold little more information than the names of bride and groom and the date. You would need to see the films of the OPRs, at a local library or LDS centre to find out if they hold any more clues.
Perhaps Margaret Macdonald and John Maclennan married later (1855 onwards) and their cert can be found on the ScotlandsPeople site. I see there is a Janet Maclennan born to a John Maclennan & Peggy Macdonald in 1855, so you may be fortuanate. The 1855 birth is worth looking at as it will contain more info than later ones.
Have you been able to find Isabella's and Margaret's deaths on SP? You can search for them using the two surnames. From these you should be able to reduce the search period for the deaths of Kenneth and John. These certs will normally give their parents names
Sometimes a look at the list of children's names is helpful. For exampla an IGI Parents search for the two pairs of names you mentioned shows similar given names for both sets of children: Mathilda, Janet, Kenneth, John, Flora. Grandparents names?
Hope some of this is helpful. Or that one of the experts comes to our rescue
All the best with your research
Catriona
