This is interesting, with the change of name in the 1901 census, presumably given by the Head of the family:

Name: John Wallace
Age in 1901: 67
Estimated birth year: abt 1834
Gender: Male
Where born: Edinburgh, Scotland
Civil Parish: Lonan
Ecclesiastical parish: Lonan
County/Island: Isle of Man
Registration district: Isle of Man
Household schedule number: 13

Ballabeg, Lonan
Household Members: Name Age
John Wallace 67 Widr schoolmaster b.Edinburgh
Margaret E Wallace 37 daur S. dressmaker b.Jurby
Sidney Wallace grandson 12 b.Lonan

Margaret's surname was "Do" [ditto], but "Sidney Wallace" was written in fully!

As they appeared to have had only the two sons William and John, I think Sidney MUST be your Godfrey?

Sue