Hi Neil,
I did try to find his birth record on Scotland's People in the hope of finding a middle name but I couldn't find a birth for a John MacLean with father Donald in Coigach 1883-1885.
However it is a tiny (beautiful) town with about a dozen families and there is an expert with several webpages who has been tracking all the families from there. This looks like the relevant census data.
in 1881
Donald MacLean Head Mar 40 Crofter
Christina Do Wife Mar 27
Alexander Do Son 8 Scholar
Johan Do Daur 7 Do
Donald Do Son 5 Do
Mary Do Daur 4
Bella Do Daur 3
Roderick Do Son 3Mo
and then
in 1891 (with Donald away from home as it says in the notes)
Christina McLean Head Mar 40 Crofter's Wife
Johan Do Daur Unm 17 Crofter's Daughter
Donald Do Son Do 15 Scholar
Mary Do Daur Do 11 Do
Bella Do Do 10 Do
Roderick Do. Son 9 Do.
John Do Do 7 Do
Christina Do Daur 5 Do
Annie Do Do 1
which agrees with 1884 birth.
cheers,
Ros