Please keep in mind that my perspective is from the other side of the fence, but here’s what I’d offer birth parents:
1. I always hated when other people referred to my biological parents being as being my “real” mom or dad. My “real” mom and dad were the ones who rocked me for all hours of the night when I had colic, walked me to my first day of school, sent me to prom, were there to hold me through broken hearts and disappointments, and were at my graduations, wedding and subsequent births of my girls. You can’t more “real” than that. Taking nothing away from my birth parents at all, my adopted parents are my real parents and you are the real parents as well.
2. It is natural for your adopted child to wonder about their genetic family. It is not a reflection on you, as a loving parent, in any way. We all have a natural curiosity about our personal history, some more than others. It is also natural for some adopted children to never pursue a finding or having a relationship with their biological family.
3. I always knew that I was adopted and I wouldn’t recommend waiting to tell your child until the “ideal” moment. That is a tough bit of news to have sprung on you at some other point in your life. My parents always told me that they “chose me” and I was good with that. My cousin was told very haphazardly as a young teen and it didn’t go over so well. Waiting can also somehow make it seem far more shameful or nefarious. It is a fact of their life and, in my view, something that should be shared as soon as they can understand the concept.
4. When it comes to details of the adoption and sharing them with your child, I’d use the same rule of thumb as you do with explaining the birds and the bees. When they start asking, start giving age-appropriate responses. Much like you wouldn’t go into incredibly graphic detail about sex and human reproduction with a 5 year old that asks where babies come from, you may not want to go into excruciating detail about specific circumstances (if you even know them) until they are old enough to understand them. I had one adoptee share that his parents told him his mother was a heroin addict and went into graphic detail about how she’d trade sex for drugs during her pregnancy with him when he was just 10 years old. Those details probably could have waited until he was a little older.
5. If your adopted child builds a relationship with their genetic parents, be open and honest with them about your feelings, as well. Adoptive parents are amazing human beings and you deserve to be acknowledged and honored in these emotional endeavors.