Actually, CRO will be zero help with a
DVC rental.
I'd recommend asking the owner to make a conference call with you. It's a simple matter for them to go through the security stuff without you on the line and then bring you into the conversation for the things that you need. It's not really an additional call if you want to add DME or the dining plan, because the owner is going to have to call anyway. A conference call would be especially important with DME, because there may be some questions about flight arrival times, etc, and it would be much better to handle it direct instead of the owner having to go back and forth with multiple calls.
Sure, the owner could cancel your ressie five minutes after your call...but they won't.
Good luck and have a great trip!