Elsie, I have a couple of thoughts - I live on the Fleurieu Peninsula where Yankalilla is. My local library has the original old BMD rgisters, which we are allowed to look at as long as we wear white gloves. Now, I do not know if Yankallilla/Inman Valley births are included - but I can find out, and on my next Library visit, I can have a look for you.
However, I do not know when my next library visit will be. I do not drive, and have to go by a very infrequent bus. But I will check when I go, then send you a PM.
I can also look at microfiche of actual certificates next time I get to the SAGHS library in Unley in the city. But that could be ages away, as I only get there once or twice a year.
Can you think of any link with what I have found? Do you have the funeral card itself - or a copy?
.....dee