Dear Aunt Debbie,
Your list of books about adoption is a great place to start. I've done a little poking around through online lists, and have found a few more that look like they might be good. Caveat: I haven't read any of these, and as Message Books, I'm afraid that some of them in full-text version may be unreadably cheesy. That being said, here are three that look worth checking out:
I Don't Have Your Eyes, by Carrie A. Kitze. On each page, the text notes a physical difference between parent and child, followed by a similarity in personality or behavior:
I don't have your eyes...
...but I have your way of looking at things.
I don't have your toes...
...but I have your way of dancing through life.
It's not the story of one white parent and Asian adopted child, as the cover might imply; each illustration depicts a different family, so a variety of races and possible family situations are covered.
Taking interracial adoption into the animal world, there's Keiko Kasza's A Mother for Choco, which follows a little fat-cheeked yellow bird on his journey to find a mother. He starts out by looking for animals who have physical similarities to him: the giraffe is yellow, but has no wings; the penguin has wings, but no big round cheeks; he is rebuffed by both. Then he finds Mrs. Bear, who takes him in with the question, "If you had a mommy, what would she do?" The story ends with Choco joining a family which clearly contains some other adopted animals: a pig, a hippo, and an alligator Mrs. Bear has already taken in. Aside from being a little concerned about the welfare of a bird in the company of a bear and an alligator, this one sounds sweet.
Emma's Yucky Brother, by Jean Little, sounds like it might be an interesting choice for Eleanor's friend, whose family is adopting a toddler this spring. It's an I Can Read book, aimed at early elementary school age kids, and tells the story of Emma welcoming her new adopted brother, Max. Max is four years old, and though Emma is tremendously excited to have him join the family, his entry is a little rough. While the reviews I've read of this one sound good, I'm a little wary of it being the kind of book which raises problems that might not come up on their own. Worth a look, though.