Well has he shown an interest in music? I think he may be a little too young for a gutair unless he's showing an interest in playing an instrument.. thats not to say you couldn't start him off on something else.
Posted by THEREALDEAL
Today, a growing body of research confirms what I sensed: There are neurological benefits to musical training from an early age, when the brain is forming. Research also associates childhood music lessons with higher grades, test scores, and self-esteem. And starting young means children have a better chance at becoming accomplished musicians, if that's where their interests take them.
But not TOO young. Teaching an instrument to a child under 3 is an exercise in frustration. Instead, bring them to hear live music. Give them simple toy instruments, like keyboards - kids love pressing buttons. If you ever played an instrument, dust it off and start playing again, in front of them.