There is a good chance the guy won't care all that much - unless he is an asshole. But since you've been talking to him for a bit, and you like him, so he is not. I am not going to say to be yourself, and things will surely get awkward but bare through it. Take it as a learning experience, even if the date absolutely bombs. It's not going to kill you, it's not going to harm you, all you'll take is a confidence hit but you will recover with knowledge on how you can do it better next time. I do suggest telling the guy that you stutter over chat. This is the first thing I do when things get a bit serious with someone I am chatting with. Once you do that, things will automatically ease and you don't have to pretend or hide your stutter in front of him.