I don't know the right answer for you, but I'd suggest talking with a sex therapist, and deciding if it's right for the both of you. I am not against spanking in relationships, but I don't believe in it in the context of domestic discipline. In other words, I'm okay with it as a fantasy, but living a lifestyle where one partner can punish the other and the other is submissive is, to me, a situation where the submissive partner lacks self-esteem and perhaps has other issues.
In any case, I think both of you should be comfortable with the decision you make, so you should make it together. You may find a sex therapist helpful in making this decision.