If I were you, I'd take off those reins and just lunge the horse. Have him put his arms out, touch the ears, tail, touch his toes, etc. Stuff to build his confidence and teach him to rely on his seat instead of the reins. I ruined my first pony's mouth balancnig myself on it and wish I'd known better.
Oh, and since he has the opportunity, he might feel more comfortable with the horse if you do a bit of groundwork first :)
Good luck! At least your boyfriend is interested in horses. None of the guys I know will touch one with a 10-foot pole xD