The artwork was recently discovered by Mrs Longley's grandson Terry.
"I came across a drawing my grandmother did in the early 1980s and, at that time, she was doing a lot of drawings for newspapers, but those that weren't published were never seen," Mr Longley said.
The one she had tagged Let's Dance had been tucked away, so Mr Longley had it re-printed onto a large canvas and gave it to his grandfather as a gift.
It features the silhouettes of people dancing and the original had been simply created by felt pen upon paper.
Mrs Langley went into Cranford Hospice for the final stages of her life and died in 2008.
Mr Langley said, after his grandfather spotted an article about the upcoming "Let's Dance" fundraiser for Cranford, he made a call to him.
"He said he felt that donating the piece to Cranford was the right thing to do - and so that's what we did."
Ms Byford-Jones said Cranford was grateful for the generosity of the Longley family, as the artwork clearly had great sentimental value.
"The fact they have donated it to be auctioned at Let's Dance means a lot to us," she said. "It is a welcome addition to our fundraising efforts on the night."
Mr Langley said that as a family they were glad to do something to help.
