My sons 4th birthday

Children as young as four can and do learn to play violin and piano. The most famous method that encourages this is called the Suzuki method and there are Suzuki guitar teachers like this group in Ottawa, Canada: http://www.suzukiguitar.ca/ The problem with children of this age is that they have a very limited attention span so the whole art of teaching music to this age is to make it an enjoyable, positive experience and a game where they get frequent encouragement for every little advance they make. I expect that your son really wants a guitar because he has seen people playing guitar on TV and has been captivated by the whole atmosphere and idea of being a top musician 'strutting their stuff' on stage! On the other hand, there is no harm at all in exposing a child to music and encouraging them to sing and play. If you are going to get him a guitar the problem will be to find one small enough for his fingers and for him to hold. I think that I would start by getting a ukelele, which is a small guitar with four strings. They are quite cheap and more robust than a guitar and so more suitable for that age. They have the advantage that they are tuned the same way as a guitar, so what he learns (if anything) will carry over to the six stringed guitar when he's big enough to manage one.

there are those guitar toys, perhaps you can give him that. so that if in case he'll accidentally break it, it wont be much painful for your pocket.. :)

It is going to be my disabled son's 4th birthday on Thursday. He has got a blue guitar operated with buttons and my children share a black guitar operated with strings. My children are quite musical. I think it is fine for you to get your son a guitar and he can play around with it. Maybe when he is at school in a few years he can learn how to play it properly.

I don't think there is a wrong age to encourage a child to learn an instrument. I got my first guitar at age 7 and I am still learning to this day. Music is a such a wonderful gift to give to a child at a young age. Sign him up for some basic guitar lessons and see how it goes, sometimes music is a passion and maybe it his. I think you should encourage him. I wish you all the best