How about starting out with the ukulele? The finger positions are the same as guitar, you just get different chords (ie, finger a C chord, you get a G). And, it's only four strings, they are easy to press down, and it is little. They are also cheap. For about 40 USD you can get a playable one. I would think that all the skills learned would translate easily to the guitar once they are old enough to handle a bigger instrument. Al