Saphron, where abouts are you? I'm newish to CO and just found out that some of the MDC mommies get together every-other Saturday at Central Park. Tomorrow, actually. There's a thread for it in the Find Your Tribe area. =)
As for having toddlers at the birth, I plan to have DS with me when this one comes along. From what I've read and people I've talked to, preparing the child is very important with videos and books. And having someone there to act as the child's doula, to explain what's going on and leave with the child if the child doesn't want to be there. My MW specifically asked that we have someone there for DS. The kid doula has to be prepared that s/he isn't there to watch the birth, but to take care of your DC and that may mean leaving exactly when things are getting "good".