We had to prepare one one for birth parents as well as kids. Of course, I am certain the parents did not and will not see it, but the agency required it anyway. Here is ours:

Dear Parents,
        We know this letter will be very hard for you to read. Believe it or not, but it is a hard one to write as well. The State has asked us to write you a letter to tell you about ourselves in hopes that it will make your transition in this situation a little easier.
        We have been married to each other for 16 years and do not have any children of our own. Adoption has been a choice for us, not a last resort. We want to build our family through adoption.
        We promise to always take care of your child to the absolute best of our ability. We will give your child every possible chance to succeed in life. We will grow to love your child and hope that your child will love us at some point too.
        We will not try to erase your childs memories of your family or time together. You will always be a part of your child; we cannot and would not try to take that away. We know that at some level, you will always be Mom and Dad to this child, but hopefully, one day we can be that for them as well. It may be difficult for you to accept this now, but God has brought all of us together for this childs benefit.
With much respect and appreciation,