I 100% agree that in a real family, candy ain't for dinner.
And I suppose I agree that in a "pure democracy" (insofar as such a thing is even a cogent thought experiment) whether candy is for dinner or not is, as you suggest, subject to a one-mouth-one-vote kind of decision procedure.

But, as you say, there are no pure democracies in the real world. My point was that in the real governments which we ordinarily refer to as "democracies," not only are some people (including minors) not permitted to vote in the first place, but even among adults some (most!) choices are removed from consideration before voting commences at all.

So it seems no more wrong to say "Sam's family is a democracy" (even though the children don't get a vote, and some choices are not even subject to vote) than to say "Canada is a democracy" (ibid).