Right, Cardinal, that’s why you rent instead of buy–trade it back in for a larger size if there’s a growth spurt (we’ve had a few of those) or, if you’re done, just hand it back and get a refund on the part of the year’s rental you didn’t use. End of problem. And I’ve heard the other kids who take lessons from my daughter’s teacher–you’d be surprised how quickly they start getting those things right, especially when they’re enthusiastic about the instrument.
Sam, this is just my personal opinion, but all things being equal, the best instrument for a kid to learn is the one she wants to learn. I’m all for piano lessons, myself, for the reasons you mention and also a keyboard helps if kiddo decides she wants to explore things like music theory. But really, she’ll sound okay sooner than you think, if she really decides she wants to play violin. But if she really would prefer piano, then that’s better. Or if she’d really prefer guitar…or bagpipes…or whatever. Of course, there aren’t many teachers who’ll give a six year old bagpipe lessons, but you know what I mean.
I’d say, if she wants to and you can afford it, find a teacher for a year, rent an instrument, and at the end of the year see how she still feels about it. Talk to her about it first, so she knows the deal–that at the end of the trial period (of whatever instrument), she can quit or switch instruments if she wants to. That way she gets to really see what it’s like and if she wants to keep going. If she does find that she enjoys violin, I think you’ll be very pleasantly suprised and very proud of her when you hear what she can do. Ditto for piano…the important thing is, it’s the instrument she wants to play.