I am in the process of adopting two of my foster children, ages 9 and 11. We live in a small town and they fear having to answer too many questions about a first name change, plus that's what we know them as. We decided (we meaning me and the girls) to keep their first and middle name, but we're adding a middle name and they'll take my last name. I agree...8 is old enough to know what they want. A fresh start is a big deal and another sign that they truly have a "new" family for older children.
