You only really have two choices, either you're going to do it, or you're not. If you are absolutely, no way, no how, going to do it then there's nothing to discuss, it's something he's going to have to learn to live without. You won't be the first wife who refused to do it. If he's a good guy, I don't think this would be a reason for him to stray.
If you're not doing it because you're afraid or its just not something you think you'll like, then you might want to do a little research on it to find the best ways to do it where it won't hurt, or at least won't hurt as much as it could. You would also have to make a deal with him that if you wanted to stop, then he would immediately stop, no questions asked. I'm going to give you a couple links to go over, and if you have any questions, please don't hesitate to ask.