Printing PNGs in book

Hi all,

I'm currenty working on a wedding album for a client, and have decided to have it published using iPhoto's book ordering system. The pages I've designed include a mixture of JPEG files and PNGs. The PNGs had no backgrounds when I created them is PS, but now I'm importing them to the book project in iPhoto, some of them are being displayed with black backgrounds, others with translucent black backgrounds and others with no background at all. In the screen cap below, you can see how three images, all backgroundless PNGs, have changed in iPhoto. The odd thing is that when I re-size the window, or enter full screen, the backgrounds change. It seems to be the biggest images are completely backgroundless, the medium sized ones have translucent backgrounds (as in the screen cap), and the smaller ones have solid black backgrounds.

When the book is printed, what will happen to the background on the photos?

Thanks!