In the situation I mentioned above, I really don't care if the school marks her unexcused or not. The trip matters to us as a family, and we're going to take it.
The day my daughter will miss is the last day of a quarter. All of her graded work and all of her exams will already be done and in the books. It won't affect her grades. The worst consequence to her would an after-school detention, which means that instead of doing homework in the library, she'd be doing homework in the study hall room. It's a chance we're willing to take.
Sometimes you just have to remember whose kid it is (hint: yours, not the school's), weigh the costs and benefits, see what can be done to mitigate the costs, and make a command decision about where it's more important for the student to be on a given day.