I’d recommend doing the opposite to what others are suggesting, be yourself. You surely don’t want to look back and think “god, what on earth am I doing?”.
Be yourself, relax and enjoy. You'll be with friends anyway. You’ll soon get used to it. After a very short while you won’t even notice they’re there. I have autism and dislike a whole raft of things, one of which is being photographed or filmed, it’s something I’ve had to endure a few times. The last time was a year ago when I did a public talk at a local gallery that was featuring my music in an exhibition. I didn’t mind the talk, I’ve done lectures before, it was the thought of it being filmed and photographed that put me off. To be honest, after a few minutes I forgot the cameras were there, the same as happened a few times, at gigs and events I’ve played at.
You need to be you though, so you’ll hopefully want to watch it again, rather than being embarrassed by some pseudo-persona that you’ve adopted.