our son who is 3 has started to stutter also. I didn't know how to respond at first but read a lot about it and feel more comfortable. We just call it stuttering and talk about it freely with him. Not every time he stutters, but just when we feel it might be worth saying. I also try to say things like "You have very interesting things to say and I love to hear it, I don't care how you say it, etc.." Mostly it has been about me trying to feel 100% ok with it and not worry, so that he picks up on how it isn't a bad thing or he shouldn't be ashamed or afraid.