ithappened - I was super worried about my older son as well, but I feel more comfortable after hiring a doula. That way, if my labor happens in the middle of the night or something, my partner can always stay with my son. My son really wants to be at the birth, but there are some scenarios where that probably wouldn't work out (i.e. in the middle of the night). My partner's mom and sister hope to be around for the birth, but you never know what can happen! They are two and four hours away. Otherwise, do you have any neighbors that you trust? If you go in the middle of the night, maybe a neighbor is willing to be "on call" to stay at your house until your son wakes up? I think if you have a scheduled c/s, it would definitely be easier because then you wouldn't have to stress out as much. You would know exactly when you are having your twins. As Leann said, the procedure is really fast. I think it took about 10-15 minutes to get my son out and I was in the recovery room for about 1/2 hour before I was wheeled into a room.
In any event, I hope you get things figured out and get the birth you want!