If you purchased 2 placeholders together, one should be in your name and the other booked as "TBA" your last name. If this is indeed the case, then yes, you can add your wife as the lead on the "TBA" reservation and book the same sailing. However, she will have to remain on that reservation. As long as you are both Gold CC members, you can book on the same day. You will also have to call to modify the placeholders when they are booked this way.