She is a tough one, isn't she? Sounds like how my W was a couple years ago.
Don't roll over. Try to negotiate in good faith, like you said you would. Ignore her jab about you again causing a problem.
How about:
"We seem to be stuck. I'd hope we can work this out in a way that's acceptable to both of us. I sent you a message on May 27 telling you about my plans for the end of June. Since I didn't hear back from you, I assumed it was okay, so I made reservations and finalized my schedule at work. I had no idea you wanted to take the kids at the end of June. It would be very difficult for me to change my plans now just two weeks away. If I can keep my plans for the end of June, I'd be happy to let you have the kids at the end of July. That way, we each get something we wanted. Can we compromise on this?"
That's the best I got right now. Good luck!
I agree. Rolling over to her demands would not be good. But I would avoid using the phrase "I assumed" in your message to her. Assuming is never good and should not be done, especially when it comes to a WAS. I would let her know a workable solution can be reached but it will only be reached by both of you offering something and not just her dictating how things will be.
This is a prime example of a WAS wanting the freedom of being single but the perks of marriage. How would you know what her schedule and plans were THIS YEAR unless things were communicated to you? Things change from year to year yet the WAS wants the perks of you knowing what is going on for her. Sorry WAS, you lost that right when you left.
To avoid problems in the future of this nature you should also mutually agree on a "deadline" to make future vacation plans w/the children as last minute changes are costly, cause conflict and make things difficult with planned vacation time from work.
