I think you need to get your Grandad's birth certificate which will give you the occupation of his father so you may be able to sort out which he is in 1911. Unfortunately his birth does not seem to be registered. Are you sure about his name, palace and date of birth?
FreeBMD has the civil registrations from when they started in July 1837 up to around 1940/50ish. http://www.freebmd.org.uk/
You can order certificates from here for £9.25 and they will arrive in about a week:http://www.gro.gov.uk/gro/content/certificates/
Searching for children after 1911 called WILSON whose mother was called MacIntosh gets these:
Births Jun 1918
Wilson Isobel C MacIntosh Llanelly 11a 2243
Births Jun 1919
Wilson Raymond A Macintosh Hexham 10b 585
Births Sep 1941
Wilson Margaret Macintosh Durham N. E. 10a 1545
Births Jun 1946
Wilson Graham D Macintosh Hull 9d 479
Births Dec 1951
WILSON John G MACINTOSH Hull 2a 307
The Births from 1941 are likely a different couple.