Yes. It could have an adverse effect upon your relationship. But that should be obvious. Hell, buying brussel sprouts "again" can have an adverse effect on a relationship. But what you really want to know is something no one can really answer for you. In order for you to answer this question for yourself, you need to consider how much you really know of yourselves and each other. When I say that, I don't merely mean the illusions we present to ourselves. I mean the real you. For instance, is your husband truly accepting of your sexual interactions or is he merely going along with your desires? Is he secretly the jealous type and, if so, how does that jealousy affect him? Some men like that they become jealous of their wive's sexual interactions with other men. Some men recognize that jealousy as representative of the fact that they love their wife and it adds to their relationship, strengthening it. And, of course, the opposite is also true, meaning that some men respond to feelings of jealousy with hostility and violence. Consider all of the particulars before doing anything. For instance, are you a dominant or is your husband a submissive? Do you have emotional feelings for the man you are planning to have sex with in front of your husband? How would your husband feel if you did have feelings for the other man? And what is going on in the mind of the man you will be having sex with? Is he simply happy to help, or is his motive something more - like an act of trying to claim you as his in front of your husband?
By raising this question, it is clear that your realize that your having sex with another man in front of your husband is not just a matter of your performing the sex act. If your husband is asking to be able to watch, make sure that is what he really wants. We sometimes lose ourselves in our fantasies and the resultant realities do not come into play until our fantasies are realized and we find they are not necessarily what we expect. So, again, I say you need to be sure that it is what you really want before you dive into those waters.