I was adopted, as was my younger brother, though the youngest is my parents biological son. As I went through the adoption process with my parents when they adopted my brother, I was fully aware of adoption by age 3. Even if my parents hadn't chosen to adopt again, I still would have known that I was adopted. They believed in being very open with all of us. I'm very thankful for that. I knew that they wanted me very much and I never felt conflicted about my status within the family. We were their kids. In talking to other family members, friends, etc, there was never any distinction made. The only time that our adoptive status came up was when it was important: doctor's visits, discussions of adoption/fertility[something my parents had struggled with]/pregnancy/etc., or when we (the children) brought it up.
Every time the doctor asks "Does it run in the family?" her adoptive status is going to be mentioned, so it's best that she's comfortable with it and that it never comes as a surprise. If you can, I'd try to work with DHS so that she does have a full medical history, but if the father is absolutely uninterested, that will be tough. As an adoptive child, this is the one thing I regret not having access to about my birth parents.
There's a book called
The Secret of Me by Meg Kearney that you might want to read. It's a verse novel told in a 14 year old girl's voice about the experience of growing up as an adoptive child (something Kearney herself did). The target audience is young adults, but my mother and father found a lot of truth and humor in it when I gave it to them a few weeks ago too, and you can hang on to it until your daughters are older for them to read. Even reading it as a 20-something, I found it refreshing. I remembered going through a lot of the thought processes of the narrator, but I also remembered having my parents around to reassure me. I called them the night I finished it and thanked them.
From what you've written, it looks like both of your daughters will be very lucky little girls because they've got a great dad