He says he's not bothered by it, the speech therapist at the school isn't concerned about it. As far as disabilities go, it's probably one of the least impactful. If I were you, I'd lay off the therapy and let kiddo know if it starts to bother him you're there him to talk to. After those conversations with him would I introduce the idea of therapy. Stuttering gets stigmatized enough, by both those with and without a stutter. We all experience dysfluency to some degree. If nobody else is bothered by it, I wouldn't pay any more intervention.