Thanks Kevin. We have to apply for them for our girls, too.
For other parents out there, we decided to go for the passport book and not the card (although as I'm writing this, I may change my mind...).
Our reasoning: If we had an emergency and had to fly home, we couldn't use the cards to fly. However, for an additional $20 per person, the cards give peace of mind to prove that you had a passport and would be helpful to prove you indeed had one to begin with. Since they are good for 10 , you never know what you'll be doing in those ten years....