My fiance is worried about making a good impression on my family from London... what can I do?

Okay, well, I have a question regarding my fiance, James. We met in sort of a strange way; I met him through a friend who brought me to a party at him and his roommate’s place. My friend ended up getting drunk and fell asleep in their living room. James and I don’t really drink much, and somehow we started talking. We spent 4 hours talking in his room after the party was over, and I really liked him. He’s so sweet, and kind, and understanding. It was really late, and somehow we started getting a little touchy; things escalated, and we actually ended up having sex (which is crazy, because I’m not that kind of girl at all. I had only had sex once before with my boyfriend of 6 months). I slept at his place that night, and since then, we’ve been inseparable (We were 21 then, we’re 25 now and we live together, as well).

Well, a lot of my family lives in London, and I haven’t seen them in ages. They’re coming to stay with the rest of our family here for a week on Sunday, and they haven’t met James. I’ve told them all about him, but he’s getting really nervous to meet them. He has mild tourettes as well (It’s nothing big; he’ll occasionally furrow his brows or roll his eyes, etc. You have to really pay attention to notice it), but it gets more frequent when he’s nervous. My family can be a bit quite to judge, which I’m not crazy about, but it’s just the way they are. So James is really worried about making a good impression, and I know he’s nervous that his tourettes will make things harder. He talked to me about it last night, and he asked me “What if I roll my eyes at some really inappropriate time or something?” So I know he’s getting really worried about making a good impression. What should I do to make this easier for him? I just want my family to see him like I do; I just want them to like him, because he’s so amazing. What should I do when my family gets here? Also, some of them are going to be staying with us (two of my older cousins), so I’m worried that things might be awkward. Any advice, please?