Photo of Grandfather or Great Grandfathers Unit

[Coral Mustang]

Happy New Year!
I am new to Canadian Insignia. There is a lot of information out there, but I am not sure I m understanding all of the changes to uniforms and insigina as they relate to periods of time and wars.
I am doing family research and have been given a picture that no one knows when or with what service it depicts. Supposedly the regiment/squadron that my grandfather, maybe GGF, belonged to, but I see there are three different insignia in the grouping- which is interesting with the gentleman in the middle that is holding the hands of the other two 'regiments/squadrons'. I am not sure what branch they represent or if it is WWI or WWII (which was what my father believes). I see differences in pockets, insignia- maybe carryovers between wars. I believe they maybe Machine Gun units- three different countries maybe from the cap badges.

If anyone can shed some light on these questions and maybe the event that created this picture would be welcome-

Thank you for any light you can shed on this incredible picture, It has really opened up a lot of interesting history for me,
P