Mason Dixon KAL

I imagine you could just scale it up. Would a larger/more active child need something more secure?

Here's a recent thread on Knitty that has suggestions for a similar sweater

http://www.knittyboard.com/viewtopic.php?t=47514
 

It's pretty easy to do if you have the child available to try it on for length. Figure out your cast-on number by measuring the child's waist and multiplying it by your stitches per inch. Then just follow the instructions, adjusting the length of the garment and depth of the sleeves by knitting more rows, and adjusting the length of the sleeves by doing more of those 3-stitch cast-ons. I believe you can eyeball it. I think it would work for a more active child (ballet dancer), provided you do not use too thick of a yarn (I think dishcloth cotton might be too bulky), and provided you use ties on the inside (as well as the outside) to hold the kimono securely so the child can move without it coming undone. Hope this helps!
 

Being a dancer myself and loving my fair share of ballet "kimono" sweaters, I would suggest a set of ties similar to a wrap shirt with the button hole on the right side for the inner string to lace through. If this dosn't make sense, go to a local department store and look at wrap shirts, it's a pretty common design and it holds up to the motion really well.