not sure i see it that way.
shooting with a rollei TLR, blad 500, giant Canon or Nikon SLR or leica M all affect the engagement and dynamic of interaction quite differently. as does waist level viewfinder, square format, vs rectangular, loud shutter, quiet shutter, etc.
Not all Canons are "giant". Most of these Mirrorless, and some DSLR cameras have tilting LCDs for waist level work, or overhead work. The adaption to a square or rectangle may be an aesthetic choice but need not interfere with how you relate to a subject.
While I do personally subscribe to the notion that a rangefinder allows you to see the world with less distractions, it doesn't mean that using a Nikon has to alter your vision or way of seeing the world around you. A decisive moment is a decisive moment regardless of the tool … be it a Hasselblad, TLR, Leica or Nikon/Canon etc.
What's the old chestnut that gets bandied about whenever discussions like this arise?
"Put anything into the hands of an experienced and talented photographer, and" … you know the rest.
But we digress … the question is about shooting family images with a M or Nikon. If the OP is ultra skilled with a M it can work. If there is a lot of activity and diverse shooting, then maybe a Nikon or Canon, or (?) might be of more aid.
I shoot weddings with a M and a DSLR. There certain things that I like doing with the M. There are certain things I wouldn't even consider shooting with a M, and I've been using one regularly for almost 40 years.
The difference is, I can't just say "darn, I missed that one" like I can when shooting my own family snaps.
- Marc