That's a real breakdown in communication on your wife's part. Someone once told me that the responsibility to get the message across lays with the communicator rather then the commnicatee (yes I know I'm taking liberty with grammar here). And it doesn't sound like your wife took the responsibility to address and clearly communicate a fairly serious issue. I can see why you'd feel the way you do.
Now that you have this dumped on you, the only thing that you can control is your reaction. First priorities first: the kids do need an accessible parent or guardian that you both trust to look after them. Independent of your anger at your wife, are the people that your kids are going to stay with acceptable to you? This is a judgement call. If you don't trust them, but your wife does, then you have to break your plans to cover her mistake. That sucks, and you certainly have every right to let her know how upset you are. It is a legitimate concern, regardless of her opinion about your fears (which could be legit, or could just be her way of justifying her actions).
Once this is all arranged with the kids, and the two of you get back home, you need to work out, in advance, what you're going to say to your wife so that she understands, clearly, that she needs to communicate with you much better. You deserve to be kept informed of all major issues regarding her plans with the children.
Take the risk of thinking for yourself, much more happiness, truth, beauty, and wisdom will come to you that way. - C. Hitchens
Me: Male, bi, 48, flexible