Hi,
Just trawling back through what's been written, they married in 1920 so the daughters would likely have been born in the early 1920's. That means they are most likely deceased by now.
You have two names from the death notice of Ivor Ling, the parents death certificates would list the other names.
If they married early you may find their marriages. Searching for obituaries on those names may find more, they may even have died earlier and you could get their death certs too.
So I think, death certificate first and see what it gets you.
Check the Ryerson Index for obituaries.
Check for marriages of the daughters, then deaths.
Again good luck
mum mum