Hi Linda
I'm not sure that I can help very much but there is a bit more information about John & Ann. The most usual spelling would be McKirdy & there is a record of a marriage between John McKirdy & Agnes Blackburn on 7 December 1828 in Barony Parish, Glasgow. Agnes is probably a mis-transcription but it looks as though John came from Glasgow & Ann from Lochwinnoch. There is a son John born 9 Sep 1834 & baptised 12 Oct 1834 in Gorbals, Lanarkshire. These are all listed on the IGI (see
www.familysearch.org) but are all extracts from the OPR, so the originals can be viewed at
www.scotlandspeople.gov.uk This is a ppv site but not too expensive if you don't get carried away. I could be particularly helpful to look as son John's entry as it will probably show who witnessed his baptism & if any of them were named McKirdy, it might give you line to father John.
Also on the IGI is a birth about 1812 in Lochwinnoch of Ann Blackburn, whose parents are shown as John Blackburn & Ann Wallace. This is a submitted entry.
I don't see any obvious birth for John McKirdy about the right time, although there are some submitted entries. The name McKirdy has strong connections to the island of Bute, so he might well have come from there. One way of trying to work out the names of his parents is to look at the names of his children. Often children were named in a particular order - 1st son after paternal grandfather, 2nd son after maternal grandfather, 3rd son after father, 1st daughter after maternal grandmother, 2nd daughter after paternal grandmother, 3rd daughter after mother. It's not failsafe but can be a useful pointer.
Hope this is helpful
Blanche