This weekend I attended the Indianapolis IAHE Homeschool Convention. I had many moms ask me questions about teaching adopted international children. Most of these moms had adopted older children [6-10 years old] from countries such as Ethiopia and other African countries. They wanted advice about where to begin with Sonlight.
I am not an ESL expert, nor have I adopted an international child, but through the years I have talked to many parents who have successfully used Sonlight in this situation. I know there are attachment issues and so on that parents need to deal with, but I am not speaking to this. What I want to offer is some help for actually teaching your adopted children when they are ready to begin learning to read, after perhaps a year of aclimating to their new family and culture. Teaching English as a Second Language can be challenging, but many have gone before you and done a terrific job of it.
My best advice is to start with P3/4 or P4/5. These contain great literature and have lots of pictures. Your children can infer a lot about the story by looking at the pictures and they will also have a lot of opportunity to gain a foundtion in American cultural literacy. By reading and discussing the many fairy tales, nursery rhymes and classic children's literature in one of these cores they will learn about your beliefs and about how the English language sounds when used in rhymes and tales, all while enjoying the brightly illustrated books.
God made us to enjoy stories-just look at the Bible--it is full of them. So, regardless of age, everyone can enjoy the antics of Harold and the Purple Crayon and Leo the Latebloomer. Also, in order to play the games that come with P3/4 a child does not need to have a great vocabulary. They can be enjoyed in any language and will improve spatial and reasoning skills.
For beginning readers, I suggest starting with Language Arts K and the matching K Readers-Fun Tales. An older child who is ready to learn, will probably catch on quickly and progress much faster than a young child. The Sonlight readers are engaging and fun and would be perfect for ESL students.
Also, ESL moms have told me that using Explode the Code works well too. If you are using Language Arts K, then you would want to use Explode the Code books A, B and C. They are scheduled in the LA instructor's guide and will help reinforce phonics in a fun manner.
I am sure you can find other advice that will be helpful too, but I just wanted to give parents an idea of where to start. Let me know if you have other questions or suggestions. I am always looking to learn more so that I can help and encourage others.