I've been riding for a while, and have recently had my first kid - a
wonderful little daughter. I want to get her started as young as
possible in the sport, so that we can go as a family (my wife rides
too). Obviously age 0 is too young , but what is the consensus (if
any) on lower-limit ages for kids and snowboards? It isn't a question
I've ever had to consider before.

Training is already beginning, of sorts, in the form of general balance
training and stimulation of the vestibular system via spinning and
stopping, jumping, etc. But I've seen very young kids on skis; I'm not
sure how young a snowboarder can be.