I’m not related to any member of this family.
1940 is the last available census at this time.
SSDI was not computerized until the mid 1960's.
ILL. Vital Records -
. Birth and death registration started in 1916.
statement source -
Illinois Department of Public Health
Division of Vital Records
Looks like you will need to order the children's death certs. from the respective county/state.
For - Charlotte B. Smith & Theresa B. Smith order the death cert. using their married name.