Trying making a request at the Welland Library; there are several newspaper articles for Isaac, and possibly death notices in 20 & 23 Jan 1939. It looks like Dorothy has an obit published 20 Feb 1941.

http://localhistory.welland.library.on.ca/newspaper/asp/


It appears the Niagara Falls Library has the obits as well.

http://www.nflibrary.ca/nfplindex/start.asp?db=cari