What I did was put my name (the AP holder) as the first name and then only listed one of the adults that was going to be in that room. (I've reserved 3 rooms.) I did list the children because that has no impact on price. I'll call sometime to update the records to put in the actual adults in each room. I think if you put in too many adults, you'll get the higher charge and you don't want that! My reservations are for February.
Also, my additional rooms (sister and her in-laws) will be arriving on the same day, but they are leaving two days earlier than us. I think that as long as they don't arrive BEFORE you, you'll be okay. It might be a hassle to hang around for them to check in, but they'll call me once they're on the way to the resort and we'll just head over to the desk around that time. We're both still working on flights, so who knows!
I received the info packet from WDW. Usually our notices are for the "XXXX Family." This time it says "XXXX Party" so it looks like they understand what we're up to.
Hope this helps.