We got each of our kids tshirts from Granola Threads (an MDC mama!) that I hope turn out really really cute! And then we bought them each one toy that they have been coveting. We did the same with DS when DD was born. Having something new gives them a distraction.
We also wrapped them each a disposable camera to use however they want to. Granted, not all the pics come out but they love to do it and it will make them feel a part of the experience.
In addition may I suggest having your DD bring baby a gift? I found that it was a nice way for my kids to appreciate their baby and show it he/she was loved. They actually had a lot of fun doing it and are excited to show baby what they bought. We just let them pick out some little thing, a teething ring or wrist rattle, that type of toy. Nothing pricey or big.
ETA: I forgot that I also made them some doll slings so they could both carry a dolly like mama will do. Even DS at 5 likes to do this when they play "house". Cute fabric, some rings, easy and small! I know that the Attachment Catalog (I think that's the name) sells them if you don't want to sew one.