Your post is old; are you still looking? 1940 is the most current USA census record.
1920 Breese, Clinton, Illinois Henry Heidel 36 Mary 34 John 13 Edwin 12
1940 Breese, Clinton, Illinois Henry Heidel56 born about 1884 in Illinois, digging coal Mary Heidel54, wife,born about 1886 in Illinois John Heidel34, son, single, born about 1907 Illinois, digging coal
1940 Breese, Clinton, Illinois Edwin Heidel32, born about 1908 in Illinois, mail carrier Agnes Heidel33, wife, born about 1907 in Illinois
Social Security Death Index Edwin Heidel born 28 Sept 1907, died Jan 1977, last residence Breese, Clinton, Illinois.
Edwin died in St. Joseph's Clinton County Hospital per his obituary. I cannot see the full obituary. It may name descendants. For a copy of the obituary write to the person at this contact address, LINK: http://archiver.rootsweb.ancestry.com/th/read/ROOTS/1996-11/15533http://archiver.rootsweb.ancestry.com/th/read/ROOTS/1996-11/15533
Agnes died 11 May 1980. Buried St. Dominic/St. Augustine Catholic Cemetery in Breese, Breese Township, Clinton, Illinois.
Also buried in this cemetery is Edward G Heidel born 07 Apr 1940 died young, 02 Jun 1958, parents Edwin Heidel and Agnes Terstegge. SOURCE: Clinton County Illinois GenWeb
John Heidel may have died in St. Louis, Missouri, 1984; I cannot see enough identifying information.