Dr. Robert H. Lewis, Fordham University, wrote up a paper called "Mathematics: The Most Misunderstood Subject." It explains the relevance of math education and learning for regular people: now I feel bad that I failed trigonometry.
The paper is a bit of a read, because he takes a lot of time to tell analogies as stories. Parables, he calls them. They are pretty informative and honest though - including where he points out that most of us will never use the quadratic equation.
His main point is that math is a way to learn how to think in certain useful ways, learning the process of analysis and deduction. It's not the goal, but a path, and learning that path means that you can work your way through to a goal well, no matter what the goal is.
It's worth cherry-picking the paper at the very least, if only to get some handy ways to explain the need for math in every day life, as well as giving you a reason to tell your kids to get more into math in school. The paper has a pretty heavy US-centric view (he says the lack of math is why the US is falling behind in areas) but it's still a fascinating read.
And I really do feel bad about failing trig in school - I went back and learned it all on my own, I promise. (Or at least, all the stuff I had time for.)