I'm a male who stutters, but I've been terrified on going on dates for years because of my stutter. All the girls I've been with have been when I was drunk and not afraid of stuttering. Anyways, about 2 months ago I went on a first date at the age of 26 with a girl I had a crush on for 6 months before. I never talk openly about my stutter to people, but I decided to on this date. She said she had noticed already and though it was cute. So my advice would be to tell him. You have to be able to be yourself around people you care about. Good luck to you