I understand what you are saying RJ. Most of the streets in that part of Govanhill have a connection to the Dixon family. Belleisle, Daisy, Gartuck and Annette streets are all consecutive to each other. Daisy and Annette must have some relevance to William S Dixon, I accept that. Its just that if Dixon did have a couple of daughters, there would surely be birth records. He married in 1851. There is an entry in the 1851 census that shows a William S Dixon aged 26 registered in the Gorbals district.
Pre 1851 birth records rely upon Church records and as the Dixons built a Methodist Church in Fireworks Village its possible that this may be the reason that no records exist in the Cof S records.
There is also the possibility of other family members having Children, Williams brother John had no interest in the family business and is reputed to have sold his shares to William.
I remember reading a claim online somewhere that Daisy was the name of Dixon's dog. I thought that was ridiculous but now I wouldn't rule it out.

Having read quite a bit about the Dixons when I was researching Fireworks Village I wouldn't either.