Letter to Bio Parent/Child

Ok, so for class we have to write a letter to bio parents and to a child. This is a generic letter that could be shown to any bio parent or child going into foster care. I am almost done with my letter to the parents but I have 1 question for you all. We are getting licensed to Foster/Adopt. My letter talks about our family and how we are here to help them through this time in their life and what we will do as foster parents to help keep them in contact with their child, that we are not trying to take their place, but to be here in their time of need (basically, in a nut shell). But I am wondering at what point do I bring up adoption or should I not at all? The instructions read "Please write a letter on a separate sheet of paper to the parents of a child who may be placed in your home. In your letter tell the birth parents some things about you and your family that would assure them of your ability to foster or adopt their child. Any advise appreciated!