First date jitters are normal

On my first date with my current bf (also, technically, the first real DATE I've ever been on as all my past relationships started with either friends or 1 night stands...) we were out for 3 hours at a restaurant... and I talked non-stop because I was sooo nervous and felt like a total idiot!
If you're already set for a date, then he doesn't think you are to young for him.

Just be yourself as much as you can - if he doesn't like you as you are, then you won't need to waste your time with him anymore!
And if you're worried that he just wants sex... then make sure you don't go to either your place or his. You'll find out quickly how things stand like that.
Try to view the nervousness as excitement - like you're about to go on a roller coaster or through a haunted house. Sorta potentially scary, but it will be tons of fun!