I have been on vacation and not able to reply. Interesting deductive work.Esther appears on a death certificate for Nancy A Lance (see below). The data was supplied by Brenda Wallace.The 1850 Census indicated that Esther Shank was age 20 at the time which would fit your theory for the unaccounted child of Daniel on the 1840 Census.
1.HENRY3 SHANK(LEWIS2, JACOB1) was born 1827 in Conemaugh Twp., Cambria Co., PA (Source: census records), and died Aft. 1870 in Rayne Twp., Indiana Co., PA.He married ESTHER WISSINGER Abt. 1847 in Indiana Co., PA.She was born 1829 in PA (Source: census records), and died Aft. 1870 in Rayne Twp., Indiana Co., PA.
Notes for HENRY SHANK 1850 East Mahoning Twp., Indiana Co., PApg. 252 Henry Shank 22 Laborer; Esther Shank 20; Nancy A. 6 mos. 1860Rayne Twp., Indiana Co., PA. Henry Shank33Farmer; Esther31;Nancy A 10; Sarah E 8; Mary 6; Joseph 3; Margaret C 1 1870 Grant Twp., Indiana Co., PApg 238 Shank, Henry 42; Hester 40; Nancy 22; Joseph 14; Catherine 10; Henrietta 4; Clara 1 mon.
Notes for ESTHER WISSINGER: Maiden name came from death certificate of Nancy Ann Lance.