DON'T DO IT, WHATEVER YOU DO. I'm serious, you will be in so much pain it won't matter how much you like this guy.
Lay down the sex law deep and heavy. If he can't handle it right now then it probably wont' get better when he gets used to seeing you around everyday. Marriage is NOT a breeding ground for romance. In fact, marriage tends to sap romance out of a previously amazing relationship.
Get serious help from a sex counselor. Insist that you both have to be satisfied with the romance thing before getting hitched. Even if you are both in total agreement about sex levels before getting married, it is likely one of you will throw that agreement out the window, just because you don't feel like it anymore. So much can happen to take it away.
Honestly, I absolutely adore my wife and we've had some great times together. She doesn't feel much for me anymore and knowing that the person you've given yourself to doesn't care if you ever share sexual intimacy again is shear agony. I wouldn't not have married if I had known this would happen. Intimate harmony in a relationship is not a extra bonus, it is a requirement.
