It would be easiest if you made it as two separate reservations, and it would probably be best to do the one night as room only.
However, about three days before arrival call the hotel directly during normal busaines hours and ask for the "rooms assigner". Remind thgis person that you have two linked reservations so they can keep you in the same room. What you would do is first thing on the second morning is check out and immediately check back in. You will receive a different set of room keys.
The only thing of real concern would be your tickets; you must buy at least one day tickets for everyone on the package and you would have to consider how to handle the first day. Of course, you could have it as a non-park day to just get settled in and visit the other resorts.