I'm also hoping to buy them through Better World Books as I love their ethics. So far I've found the following that look good:
- That's Why We Don't Eat Animals
- Baa Humbug!
- Farmer Duck
- Hubert the Pudge
- The Magic Finger
There is a HUGE LIST here thanks to vegbooks. I've just listed the ones that I liked the sound of most. Feel free to leave a comment about which book/s you like the best for your children/cousins/siblings :).