Some info you may already have:
The only IGI IOM marriage for John Sheard between 1800 and 1841 is with Elizabeth Corkil(l) on Dec 26 1811.
There is a John Sheard (75 pensioner) living with Julia (Judith in 1851) Sheard, 48, Daniel Sheard 15 (son or grandson?), and Joseph, William and Benjamin Garry (Perry in 1851).
There is an IGI marriage on 11 Nov 1839 in Braddan between a John Sheard and Judith Perry or Quirk.
The children of Elizabeth Corkill and John Sheard, including a James Sheard, were all born between 1812 and 1823.
I saw no pre 1839 burial record for Elizabeth on Brian's site.
However also in the 1841 census in Douglas, there is a James Sheard (39), Elizabeth Sheard (29) and Ann (11 months).
The IGI has a christening of Ann Sheard in Douglas on 16 Aug 1840, daughter of James Sheard and Elizabeth Cannell.