I second the PP's reco of the book "my new baby". I have the Kubler version but the new Fuller one looks good too. I like that they show mom nursing baby while just going about daily life. That's what goes on in our house so it was good to show those pics to DD. There's not much you can do to prep them...it will work itself out in time. One good thing if you are nursing (or even bottle feeding in the beginning you'll need this!) is to have a tub of small toys that are new that are only for when you are feeding baby. This way they will keep your older DC occupied and happy while you spend endless hours feeding....
M, mommy to A 2005, E 2007, and L 2010