Don't get baited into an argument with no potential for a positive outcome. Just do what you do and keep your cool. You have every right to your plans as she has to hers, and there is no duty on your part to try and anticipate what she wants.
I vote you keep your plans with the kids and be cordial and unemotional about it if she has a problem with that. That's HER problem.
-PM
M:12y - BD:12/11 - D:6/13 - 4Ds
"The ultimate measure of a man is not where he stands in moments of comfort and convenience, but where he stands at times of challenge and controversy." -MLK Jr.