I looked up Nora and John and didn't find their death info assuming they stayed in Santa Clara Co.
Did you look up Nora or John in whitepages.com? A long shot now that everyone has cell phones.
You can order a copy of Frank's obituary if you have his death date (at least the month and year) from the Silicon Valley Library System, obit.systemref.org. They do charge a fee but that would give you a better idea of where Nora, Patricia (hopefully with her married name) and John were living then.
After I find more current living location, I use zabasearch.org or look up the person in Facebook.com. Successful Searching!