Does he ever express frustration with his stutter? You can try bringing up the topic with him to see how he feels about it. My personal experience was that, at that age I couldn’t enunciate certain sounds and when I went into speech therapy I felt a bit like my parents were trying to fix something about me that I didn’t particularly see as an issue, and the stress of the whole thing (and an admittedly less that stellar speech therapist) ended up with me leaving speech therapy with more speech issues than I went in with. My experience isn’t the common experience— a lot of kids go into speech therapy and learn ample coping methods to work through their stutters! I would say the vast majority probably have positive experiences with it, but I would say at his age his opinion should be considered before making a definitive yes/no to speech therapy, and that communication on your end to him as to why you think it would be a good idea (without insulting his stutter or making him feel ashamed of it) is key.