Hi Chas,
I am a canon user, with some Sigma lenses. I have to be careful which Sigma lenses I get as some will not play nice with canon cameras.
I don’t do weddings and have respect for those that do. I am better as the informal friend with a camera that captures those moments that others miss.
Sounds like your style is a mix of the two, and it sounds good fun.
Sigma lens wise I have an old style 150 600 5.6 zoom that I got at a silly price because the chap in the shop thought it was a telescope and there were bits missing. I took a chance and it’s turned out ok.
The combo of the 600 end of the zoom and the F 5.6 limits it’s use a bit as I have the 1.6 crop and this brings minimum shutter speed up to 1/1000 of a second .