Hi from another mom to a bio daughter (age 3 1/2). We found some great books for siblings of adoption to explain the process to her - recommended from friends who adopted from China:
"Seeds of Love" by Mary Petertyl
"Things Little Kids Need to Know" by Susan Uhlig
"My Special Someone: A Child's Perspective of Adoption" by Brittany & Sherry Kyle
Our daughter loves "Seeds of Love". It's about a little girl whose parents are adopting internationally - they travel without the little girl to bring home a baby girl, so the book also deals with separation while parents travel. It never mentions what country the baby is from. We are adopting a boy, so we just read "baby boy" into the story and it works fine. Our daughter now "reads" it to herself because she knows it by heart, and tells everyone that she's adopting a baby brother from Russia. The book really helped her understand that we'll be "having a baby" differently.
"Things..." is also very cute - about a little boy telling all the things he will "teach" his new sibling. I liked that the two books dealt with different aspects of adoption for the sibling-to-be!
"My Special Someone" is written by a 6-year-old who describes the process of adopting her baby sister from a kid's point of view. We don't have that one, though.
I bought the two I have online. Good luck!
- Maura
