Each of you, to your own parents, "Look, Mom, Dad, we love you, but you gotta check in with us before you book tickets. If we know in advance, I can plan to take a day off with you, and we can make some fun plants. But this booking flights and then telling us just isn't working. Can you help us out here?"
And then, if they do it again, "Mom, Dad, I hate to do this to you, but that's going to be a terrible week at work, and we just can't do a visit then. How about *suggest a long weekend a few weeks later*?"