I think it depends on your children, their ability to cope with new situations, and your own comfort level having them at the birth.
I've had my oldest son at all 3 of my subsequent births, and my last birth was attended by all three of my older children. We prepared by watching birth videos borrowed from hospital childbirth class, and reading books, and talking about what would happen. I also always brought along an extra support person just for the child, so that they could be free to come and go as they needed, and dh could focus on me. At this last birth, my oldest ds, who was almost 15 and a veteran of 2 previous births, was in charge of the littler kids. He did a great job with them.
I loved having my children present, and having them get to touch the baby when she was so new. We are not a very modest family in general though, and I know that my natural style in labor is pretty quiet and not likely to scare my kids.
I'd also talk to your care provider and see if they have experience having children present at birth.