As far as telling your wife, start with fantasizing about adding another man while you two have sex. While enjoying doggie style, talk about having someone lick her clit. If it turns her on, then reverse that saying that you would love to clit her clit while another man is deep inside. Start with fantasy then slowly build off that.
If you have sincere concern that you may get jealous, that is a real risk. I had been with many men, women, and couples over the years, with hubby watching, participating, being cuckold, etc. He loved it. However, he struggled when I went black because he had never seen me having multiple squirting orgasms. And needing it more and more. He asked me to stop; I couldn't. Don't go down this road unless you are sure. Over the years I have seen my share of fights when the wife enjoyed sex with someone else too much.