I could joke that few family histories that I have seen have had any historical understanding, but maybe that is too near the bone.
King G 5 and Queen Mary did visit the Island for 9.5 hours in July 1920, the report does not mention any visit to Bishopscourt where the Bishop was Dr Denton Thompson - No member of the Cannon family has been a Bishop on the Island - some members were strongly associated with the Mormons however.
A good reference might be 'Here is the News: A Chronicle of the 20th C - vol 1 1901-1950) ISBN 1 873120-42-7 - you could try various Island bookshops - see Manxnotebook site from head bar above under organanistations/publishers etc for web addresses