Have been doing some more digging - from the IGI worked out that John's mother Elizabeth FERGUSON: her mother was one Isabella BROTCHIE who was born in England abt 1810 and her father was a John FERGUSON.
Can find Isabella and children on the Census 1841 to 1881 - and she's living for the most part either with or next door to Elizabeth. I can post the Census here, if anyone wants or else I'll just send it to Stephen by PM
The most interesting thing to come out ot that is......at least 2 of Isabella's son's (Elizabeth's brothers, John's uncles) are Watchmakers and Jewellers in Inverness. One of them James, at age 26 was an employer of 5 men and 2 boys in his business. So that is obviously where our John MacKENZIE 'inherited' his first career - possibly apprenticed to one of his Uncles, probably James, Can't find out if his grandfather John FERGUSON was also in the same trade - think he was dead by 1851 and I can't find them on 1841 yet.
The MOST interesting thing is: I think James FERGUSON became notable in his trade and is the maker of a fine clock listed here, for sale :
http://www.ianburton.com/shopdisplayproducts.asp?id=1&cat=Latest+Stockhttp://www.antiques.co.uk/antique/Antique-Scottish-Longcase-Clock-2"Antique Scottish Drumhead Longcase Clock.
James Ferguson, Inverness.
Circa 1880 - Rare, corinthian column mahogany case in nice original condition"
"James Ferguson is recorded as working from 1886-9 in Edinburgh and from 1872-81 in Inverness. He received a Royal appointment to Queen Victoria in 1872" And , if you've got a spare 7500 quid, it can be yours!!

Also found Naturalisation records in the US for John's children:
Gerald, Ian/Jack, Allan, Arthur, Lillian so far - no doubt it's them, since they all reference their immigration into the US on the "Majestic" on 8 May 1913 with Mum, Effie (which we have found earlier in this topic).
As part of Ian's Petition for Naturalization, he requested his name be legally changed to "Jack MacKENZIE" this was granted when he swore the Oath of Allegiance and was Natturalised in 1927.
I also discovered, Lillian did marry - to a man also surnamed MacKENZIE. Not sure if she had children. In 1930 she was working as a Film Cutter in a Movie studio.
Arthur was not 'in the business' and was a Tax Agents assist.Clerk/Secretary in varying records.
Now after all that - I have found a tree on A* descended from Allan MacKENZIE, John's son. ( I checked A*s trees early in the piece when I still thought John was born abt 1867 and had a wife named Ida - and didn't look again till now). And Yay!
This tree, also places John as the son of William MacKENZIE & Elizabeth FERGUSON (and names Elizabeth's mother as Isabella BROTCHIE). It references some BDM dates, Soc Security records, Cal. Death records etc and takes the lines back beyond John a couple of generations in each case. Some of it may have come from extracted IGI records, but some of the death dates can surely only have come from a Scottish Certificate so I feel the tree is entirely accurate as presented. In each family on the tree only one child is named - ie: John FERGUSON & Isabella BROTCHIE - dau: Elizabeth, William MacKENZIE & Elizabeth FERGUSON: son John, John MacKENZIE & Euphemia CALLUM: son Allan. There is no biographical information, no Census have been quoted.
The tree descends to present day to someone - the tree owner - who is listed as 3x grandaughter of John.
Allan MacKENZIE, was unmarried & a Cameraman when he was Declared Intention for Naturalization in 1922. Assuming the tree is correct by 1930 he was married with a son and was no longer in the movie industry, he stated he was a Salesman in a Cotton Mill.
Given the propensity for living to old age, I would say there is a good chance some or all of Gerald's children or Jack's children are still living - for that reason, even though we can find them on the 1930 Census, we shouldn't really be naming them on here?

Allan's son as named on the tree is deceased, in 1998 in Washington. But
his son and grandchildren are living - the tree owner being one of those grandchildren.
I will PM you Stephen!
PS; According to the A* tree - there is a connection for John's family in Aberdeen (ref: Harry de Windt's book) - his wife Euphemia CALLUM's mother was born there, and her father before that.
Cheers
AMBLY