Hi, I'd like to help you with your question.
It all depends on how you feel about the suggestion. If your husband is serious, is this something you want to do? If you feel uncomfortable in any way, then it is not ok to do.
Married couples often use fantasy and other supplements to their sex life to keep it interesting and fun. The rule is that as long as both partners are comfortable with what is happening and no one is getting hurt, then it is alright. But if one person has any reservations, they should not agree to it.
The problem comes when one of the partners feels guilty, forced or obligated to give in. Then once the act is over, that person starts to pull away from the relationship because of how they feel. It creates a rift and problems can begin that are hard to resolve.
If you find that your husband is insistent or otherwise tries to coerce you, then you may need to talk to him about counseling to resolve why he feels he needs to force the issue.
I hope this has helped,