With all my kids, we watched the baby shows on TLC...cheered when the babies came and I answered all their questions about the mommy and labor. In my opinion, even at your daughter's age it is wonderful to involve them in every aspect. Even delivery. I always had someone that could be there just for my kids. If my kids wanted to leave that was their choice. None ever did. They were there to be the first to hold their brother or sister.I really credit watching the shows together as a big help. Hospitals have sibling classes. Birthing classes were family events for us as were every sonogram appointment. Libraries are excellent sources for books and videos. Make a Big Sister shirt and tote bag to take her favorite toys, books, crayons, and movies to the hospital. (Michael's will usually have tshirts and canvas tote bags pretty cheap) With my youngest, she was 1 when her sister came, I played with her baby dolls and fed them and hugged them-just to show her how to hold baby and we changed it's diaper...just things like that. I got her a baby chou chou doll, she cries, and goos and laughs. You have to do something to the doll (feed it, burp it rock it)for it to stop crying.
I know 2 1/2 seems young to be in the room when you have the baby, and by all means it should be your choice, you know your daughter best. You might even ask her. If you do decide to, tell your OB, as long as your OB agrees, the hospital will allow it.
I remember being taken to my grandparents when my brother was born and then when he was sick. I never wanted my kids to feel left out. It was great for our family but doesn't mean it would work for all families.
oh and most Libraries have online catalogs and you can search for books (just quicker to me) and videos.
Congrats! Good luck!