Hi, Sue
I agree that Elinor ch 1803 d/o Charles Shimmin/Elinor Cowle is the likely wife of John Shimmin.
Note one of their sons is named Charles--a not so common name but certainly not rare.

Peel Monumental Inscriptions
Old Peel
#281
Charles Shimmin of Eary Voare who died De'r 17th 1831 age 56 years
Chas Shimmin son of Chas & Elin'r Shimmin of Eary Moar was buried the 2nd day of Nov 1801 ag'd 2mths

Don't see a likely Elinor in the burial register or MIs