8 years old is a great age to begin speech therapy, he will be aware but still malleable. I'd strongly suggest looking into it. What's his opinion on speech therapy? Speech therapy impacts every patient differently. For me it wasn't particularly helpful but for him it might prove to be very valuable. As well as this, maybe get some advice on physical tricks, perhaps his posture could be improved a little if possible to improve his air intake? If not then obviously there would be other techniques. As for his feeling maybe sit and have a conversation specifically about that. Ask how he feels about his stammer or how he feels it impacts his relationships. If you haven't done this up until now then just make it obvious that he doesn't need to worry about it around you.