You know, when I read that first post yesterday about this sitch, I immediately thought the same thing your W did, that this was really something you were going to do for the kid's sake, not really her's. After reading more, I understand the distinction and I have to say, it's a REALLY tough call. I'm SURE there are a ton of people out there for whom this would NOT be a tough call at all. I would even say many on this board probably feel like you should take a stand.
I FEEL like you should too, but fully understand your hesitation.
Here's the thing. Your W's perception is VERY skewed these days. She is NOT making rational decisions. That said, your letter to her IS judgmental and the work thing added in just sounds like an excuse to me.
Let me be perfectly clear. I say you are being judgmental FROM HER PERSPECTIVE, which I assume you were concerned about. You are most certainly judging this action of hers morally wrong and thus "want no part of it". Well, IT IS MORALLY wrong, but then again, so is the affair as a whole so this distinction seems a BIT arbitrary to me but then again, an overseas trip to consummate a EA seems a pretty good place to draw the line.
I think you have decided this is a boundary for you. I actually think you have made the trip a boundary but haven't come to grips with what it means to you yet. This idea of not taking the time off IS your attempt to try to thwart her plans, and even if it isn't,it looks to all the world like it is. I say more power to you, just understand that it could backfire.
Muddle, I wish I could offer you some solid advice here, like you have to me recently. I just cannot. I don't have a CLUE how I would deal with this any more than you have a clue how you would have dealt with my sitch of W going out 2-3 times a week to see OM. I THINK I know what I would do, but clearly, I am not in your shoes and cannot seem to put myself there.
I guess the only thing I can add, other than more confusion and second guessing, is that maybe it would be best to simply say you are not taking the time off, period. Don't explain yourself or try to justify anything. To me, it really won't matter what you say after "I'm not doing it" because she'll just try to turn it against you and make you feel like an a-hole. Why not let her come up with her own reasons for that.