I’m not related to any member of this family.
You wrote - "They had three living children - two b. in NY and one in MI. I have not found them in an 1850 census."
Wha makes you sure these children were born in NY & MI since the 1850 census is the 1st census to list/show birthplaces???
Michigan did not require “by law” birth, marriage & death registrations until 1867.
TRY - Find a grave – FREE SITE - volunteer site all states; frequently has headstone pic
DO NOT SEARCH FOR A MARRIED WOMAN USING HER MAIDEN NAME.http://www.worldvitalrecords.com/
Try Vital Records – Birth, Marriage, & Death, Social Security Info., Census Records – FREE ALL STATEShttp://search.labs.familysearch.org/