"What? Will I have sex with him? Well -- I really think he does expect that since we'll be sharing one hotel room the whole time -- and it's probably something he really needs now, but I promise I'll ask him to use protection. So like I said -- there's no reason for you to be so jealous about it."
Even though your wife seems to think that all she's doing is being a good friend to him, you still can't help feeling jealous and hurt, but there really isn't anything you can do without seeming to be a real jerk about it. It's just that you had always thought that you would be the one who would take her to Hawaii some day, and that it would be a really romantic place for the two of you to visit together. And now you have the pain of thinking about it being a romantic vacation for her -- but without you.
Your wife convinces men to forget their wedding vows
This is certainly not the kind of marriage you had ever thought you would have, but she long ago made it clear that this was the only kind of marriage that would work for her with you, and so you have no choice but to accept that this is how things are. A few times, you've come close to complaining about the fact that she leads an active social -- and sexual -- life with other men while you almost never go to social events and you're sex life consists of occasionally being permitted to play with yourself. But you knew that if you did say something, it would anger her, which is the last thing you want, and so you simply accept your lot in life as her cuckold.
When you urged your wife to start taking tennis lessons, you had no idea that cuckolding would quickly become part of her weekly routine with the local tennis pro.