They really twist around on the kids. I know with mine they did. Get the longest you can that doesn't crimp the elbow and maybe you have to cut and redo the straps if you can't get them short enough. If you have a lace model that's better.
Nothing will turn a kid off shooting more than getting his or her arm wacked by the string. That stings. That and bad criticism. Protect their arms and praise and award any progress they made. I took an old arrows, cut them down and retipped them, sprayed them with gold paint. Mounted them on a gold painted block of wood. Every shoot we did they got another gold arrow to put on their dresser. Nice way to get rid of broken arrows too.
sam