Grandparents as reality, not theory

I am not particularly mystical or sentimental about genetics. I favor openness. But I just started getting my daughter's results back from 23andMe, and some of her coefficients of relatedness to her grandparents deviated sharply from 0.25. As I have blogged about this possibility I was obviously aware of the abstract probability here; but it is a different thing altogether to be faced with reality. How exactly does one go about explaining that one of your parents is ~50% closer genetically to their grandchild than the other? I don't think it matters really in a concrete sense for them, but divulging this information makes me somewhat uncomfortable. Many, many, others are going to be confronted with these issues. We don't have social norms yet. This isn't cut & dried like paternity. Thoughts?