"I hope it works out for you and OM"! "You deserve to be happy", "I think I'll take our kids out for ice cream, have a nice day", it sure can't hurt, right?
A few months ago we had a talk and I told her that if OM is giving her the emotional support that I failed to give her over the years, and she is happy, then I respect their R (basically saying that I respect her decision -- even if I don't like it, agree with it, etc). I then added that I just want her to be happy, at which she said that she wanted me to be happy too.
I think doing this is beneficial in the long run because it shows letting go and unconditional love. I said it in a way that was sincere and didn't come off like a guilt trip, and it will give W something to think about in the future.
How long have you and your W been separated? I understand your need to get a self-esteem boost by not wearing the ring on vacation, but I would caution against it. Boost your self-esteem in other ways. If you're invested in saving your M, do you not think that taking off the ring for such a purpose is an ethical breach?