Hello Aeroqueen, I am sure that this is not going to help you at all but ...
I can't find any trace of your Gardners either. I looked through the 1881 census index for Bonhill to see if I could find anybody living at Gardiner's Land in 1881 and I found this:
living at Gardners Land, Susannah St, Bonhill,
Elizabeth Gardner, a 74 year old widow, annuitant born in Leith, Edinburgh with her daughter
Agnes A. McGown, also a widow, teacher, aged 47 and born in Alexandria.
Elizabeth McGown, single, granddaughter, a 17 year pupil teacher, born Glasgow
Jane McGown, single, granddaughter, a 15 year old scholar, born Glasgow
James McGown, single, grandson, a 13 year old scholar born Queens Park, Renfrew
Gardner McGown, single, grandson, an 11 year old scholar born Queens Park, Renfrew
Mary McGown, single, granddaughter, a 10 year old scholar born Queens Park, Renfrew
John W. A. McGown, single, grandson, an 8 year old scholar born Queens Park, Renfrew
Edith L. Airlie, single, granddaughter, a 17 year pupil teacher, born Canada (British Subject)
Elizabeth Gardner (aged 74 above) was Elizabeth Waits married to James Gardner, 30th November 1833 at Bonhill (IGI extracted). I checked for the death certificate of James Gardner - he was an Ironfounder, married to Elizabeth Waits, died aged 67 on 24th December 1874 at Alexandria, son of James Gardner (Blacksmith deceased) and Isabella Gardner m/s Finlay. Cause of death: Dropped down dead at his work, supposed to be heart disease. (There was an RCE but I can't read date details).
According to the IGI, James was born 15th Jan 1897 at Bonhill. Other children of James Gardener and Isabella Finlay (married 19 Oct 1799 in Bonhill)
Lousia (sic) Gardner, b. 20th Sep 1800, c. 9th Oct 1800 at Bonhill
Andrew Gardener (sic) b. 14 Jun 1809 Bonhill
Agnes Gardner b. 24th Feb 1802, c. 21st Mar 1802 at Bonhill
James Gardener b. 15 Jan 1807 at Bonhill
Cathrine Gardener b. 19 Jun 1804 c. 25th Jul 1804 at Bonhill
Obviously I was hoping for a John Gardner also but no joy although I did find an Isabella Gardner on the 1841 census living at
Stony Mollen (?), Alexandria, Bonhill
Andrew Gardner aged 70, Farmer born Outside census county
Isabella Gardner aged 75, born in Dunbartonshire
Jean Gardner aged 45, born in Dunbartonshire
Isabella Gardner aged 35, born in Dunbartonshire
Robert Gardner aged 30, Ag Lab, born in Dunbartonshire
Living next door to them is a Mary McNaught (sic) aged 75, born outside census county.
When I checked into Andrew Gardner and Isabella above, I think that Isabella was Isabella Glen and if so, Andrew and Isabella did have a son, John Gardner born 7th Aug 1804, c. 17th Aug 1804 in Bonhill (is 1804 about the right time period for your John Gardner??).
Also by complete coincidence, I think that this Isabella Glen belongs to me (big surprise!!). I haven't confirmed it but she could be my 6G Aunt, Isobel Glen, daughter of my 6G grandparents, James Glen and Jean McIntyre (married 16th Dec 1758, Luss, Dunbartonshire). If so, she would be the sister of John Glen, my 5G Grandfather who married ... a Jean Gardiner and had 5 children in Bonhill.
Any of these names mean anything to you?
regards,
Lindsay