If it's a well-behaved kid, I think it's fine. People staying in huts pretty much all have earplugs anyways, and as others have said, adults can be noisier than a kid in there - snoring, people getting up at 2am for alpine starts, obnoxious grown-ups who bring iPod speakers, etc. That said, I think I would be a bit annoyed if someone brought a kid that they know cries all night non-stop. Apart from that, I think it's awesome that you're doing this and getting the kid introduced to the great outdoors at such an early age :-).
And for what it's worth, depending on what outdoor activities you're after, Stanley Mitchell may be the nicest hut with a kid if you're staying more than a night and just want to take it easier. It has the meadow, so easy to take simple walks, etc.