Or you can hand out books that are geared to friends and relatives of prospective adoptive parents. When Friends Ask About Adoption by Linda Bothun. Both are available through various book stores and adoption book catalogs. Give them time to adjust. Don't give up, and keep trying to build bridges.
Most people come around eventually.
And never lose your sense of humor. It may be your best defense. If your parents have a negative reaction that doesn't change over time, know that they are saying something much more about themselves than they are about you or the child you are planning to adopt. If you have done all you can, then hold your head high and let it go. Check back soon for more answers to your Frequently Asked Questions.