I only read the original post in its entirety, and scanned the responses, so I may be double here.
WTF???!!!!! What are these people thinking?????
It's YOUR baby. They had their babies, and their chances to have a circus in the delivery room (bet they didn't like it either
). I would just tell them, matter of factly and in a way that makes clear that there's no sense arguing, that they will all be welcome after the 24 hours (or whatever) that they UNDOUBTEDLY understand are necessary for family bonding. And if they don't understand that, they need to grow up already.
And I hope your dh will come to understand that this is HIS baby too, and that HE and not his family gets to decide what happens. Maybe you can make him see that being born is a big enough transition as it is, and that seeing 15 strange faces makes it that much harder for the baby to identify the most important ones, namely those of parents and siblings???
good luck. And enjoy your birth!!