He seems to know what he wants. If it's what your wife wants, I don't see where it's up to you anymore. Just enjoy the ride. If he's a serious bull, you must respect his wishes. Happy wife/Happy Life still applies here. You may want to discuss with him the clear boundaries of your restrictions. He may allow you to have sex with your wife once, before he has her.
If I were him, you would have to use a condom...and not be positioned face to face. Also, no longer than 5 minutes to fuck, so work fast! You becoming the best cuck you can be, is top priority.