Hey man I was there once, too. As it turns out, her parents are probably going to like you A LOT. They are honestly not going to think badly of you because of your stutter, so don't be afraid to talk to them. If anything, most people probably see our stuttering as a disarming trait. Chances are, in their eyes, you will come off as this nice, quiet, thoughtful young man. Despite what people lead you to believe, being quiet can really be a good thing (In my experience, it's preferred over the loud and boisterous guys). So don't sweat it! Be yourself. Be courteous, say please and thank you, smile a lot. Most importantly, have fun!