First step in finding their descendants is to identify their children. You did that already - bravo! - and posted on another forum.
CHILDREN of Thomas and Agnes Anastasia (Connors) ALLEN of Hibbing, St. Louis, Minnesota: John Allen, Marie Allen, Helen Agnes Allen b 11 Jul 1920 in St. Louis County Thomas Dayton Allen b12 Oct 1922 in St. Louis County Edward Allen b 04 May 1924 Robert Francis Allen b 02 Jul 1925 in St. Louis County Elaine Mae Allen b 07 Jun 1927 in St. Louis County Sarah Allen b 23 Mar 1932 in St. Louis County
Next step would be to identify their spouses - and maybe you know them too?
As for finding Mary Flannery's ancestry, please state the facts of her life for us! Your post reveals you know much more than you said. Tell us, puhleeze?