I want to share my fantasies with my partner but I'm embarrassed. How can I share that side of my sexuality with them?

My wife and I experiment sexually and want to expand a fantasy where I watch her with another man. We thought of getting a man though a website search, someone who would be willing to do everything except go all the way and practice safe sex. We are very happily married and this would satisfy two of our biggest fantasies. Me seeing her with another man and for both of us being watched by him as we want to have him watch as I.ll step in to finish as we decided he wouldn.t have actual intercourse with her. My wife will take care of him for his services with oral or manual sex. She is totally into it but she is actually worried I might have some misgivings about it later. So before we actually engage in this activity I thought I'd ask if there were any pitfalls we might encounter.

SS in SF