I have loved having my children at the birth of their siblings. there are many resources that can help to get your DD acquainted with the whole process and get ideas on what it's like.

we read 'hello baby' by julie vivas (i think that is her name?!)...not the mem fox book of the same name...

I also went on a search of really cool birth videos that were calm and reflected our births and intentions. I particularly kept my eye out for births that had other children in them. one i think that is brilliant is 'my easy birth' on youtube (i think that is the name). and a BBer on here has a gorgeous one on youtube with her DD in it. i think she has posted the link somewhere in the HB section.

it really is amazing having your kids there. i have loved it and the girls have loved being part of the process (although my DD2 missed the most of the birth of DD3 but did some good back rubs during the day lol).