With almost no exception, speaking even when you don't want to is the best choice for stutterers. I would highly, highly encourage him to do his speech just like everyone else. But it's also important to realize that sometimes stuttering can be physically painful, and he might already have a strategy going, that's working, and the speech might throw it off. I'd talk with him personally and encourage him, but be understanding if he's strongly against it. If it's just nerves, don't let that slide, haha. If his reasoning is deeper than that, do as you see appropriate. Also thank you for asking us in here, it means a lot to see a teacher care. 🙏