One of the most pervasive errors in creation science textbooks relates to geology. Young-earth attempts to account for practically every geological event within the span of a year during Noah's flood is simply unsupported by the fossil, geological, and geophysical records. Their approach can sound plausible to the untrained, but with the exception of only a few, those who have studied geology on a more sophisticated level find these claims untenable. Unbelievers find them laughable.
But what should regular, everyday Christian parents do? Most don't have the education to adequately judge the debate - who is right and who is wrong. I would like to gently suggest that if you are using a creation science textbook that you take some time to read through the opposing position, namely old-earth creationism. God is a God of truth. His people should be willing to pursue truth no matter where the evidence leads. Consider what a positive example this will set for your children about the fair-minded nature that Christians ought to have toward opposing viewpoints. We can investigate arguments fairly without needlessly lambasting people, while at the same time searching for truth and understanding our own positions better. Also consider having high school aged students investigate both sides of this debate. It would even make a great oral debate project for a co-op.
Here is a great page of resources that address the many problems with global flood geology to get you started: "Noah's Flood and Creation Science". I realize this page could seem daunting, but it will give you some idea as to the wide variety of responses that are available on this important issue.