You don't have to discuss your crazy Aunt Janice's numerous run-ins with law, her questionable taste in men or her unbearably tacky lawn ornaments, but you should probably disclose her clinical depression. And the fact that she's a hoarder and a cancer survivor.
We all have family skeletons, and while you don't have to open all your kin's closets, it's important to reveal any medical-related issues, especially any diseases that are or could be hereditary. Your son's wife is going to be the mother of your grandchildren, so it's only fair that she knows what she's getting into.
Of course, you can also point out the thick head of hair your husband still sports -- good traits are important, too.