Many thanks for the pointers Jim. It almost certainly rules out the possibility that the woman is Jane McCracken.
I too had thought that the woman in the pciture was into her late 60's or early 70's whereas Jane died aged 45.
The source also stated that the children were her grandchildren but Jane's grandchildren were all born after she died. Her husband remarried the year after she died in 1872. Her children would have ranged in age from 2 to 16 at the time of her death.
Once again, many thanks.