Great suggestions. I would add:
I'd get multiple copies (2 or more) of So That's What They're For! and The No Cry Sleep Solution.
Birth:
The Business of Being Born dvd (so people can check it out and watch it)
Breastfeeding:
The Ultimate Breastfeeding Book of Answers (Newman)
Medication and Mother's Milk (Hale) - as a reference
Milk, Money, and Madness (Naomi Baumslag)
Breastfeeding: Biocultural Perspectives (Katherine Dettwyler)
General Parenting:
KIDS (by Meredith Small, author of the pp mentioned Our Babies, Ourselves)
Nurture Shock (Po Bronson and Ashley Merryman)
Siblings without Rivalry (Faber and Mazlish)
Diaper Free (about EC) - if you think people would check it out
Babywearing (Maria Blois)
Child of Mine,
How to Get Your Kid to Eat: But Not Too Much,
Secrets of Feeding a Healthy Family, and
Your Child's Weight: Helping, Not Harming [all by Ellyn Satter]
For Allergies:
The Culinary Guide to MSPI (Wise)
The Milk/Soy Protein Intolerance Guidebook (Field)
The Complete Food Allergy Cookbook (Gioannini)
I have not yet read Born in the USA: How a Broken Maternity System Must be Fixed (Marsden Wagner) but have heard it recommended and it's on my list of books to read.
My favorite pregnancy book was The Mother of All Pregnancy Books (Douglas) - more mainstream, but IIRC she still is very supportive of NCB, breastfeeding. I think she was neutral about circ (Pros/Cons list). But I liked it way more than the WTE books.
Good kid's books for AP/Breastfeeding stuff:
Will There Be A Lap for Me? (Corey)
What's Inside? (Ashbe)
Sophie and the New Baby (Anholt) (all three of these feature breastfeeding)
Everywhere Babies! (Susan Meyers)