You've already received great advice above, but I'd add one more thing, based on my experience as a book club member (as an adult) - feed them dessert! Maybe have something like ice cream + toppings they can add, or decorate a cupcake or something. I know that has *nothing* to do with book content or high level book discussion, but it goes a long way to breaking the social ice
My other bit of advice - also based on my book club experience, so take it for what it's worth - let the girls wander off topic if their conversation goes there. I'd look at this as more of a social adventure than actual academics, so it's going to be ok if they talk about things other than the book.
Have fun with it!
polarbear
ps - another thing you might do is let the girls choose the next book they read (you'll probably choose the first?). You can have a selection for them, but let them choose.
