Not even able to attend, so don't mean to butt in (guess I am anyway, though!) LOL, but I was thinking "If I were ABLE to attend, I sure wouldn't want to miss any part of a "once in a lifetime event", especially for a dinner that can be had at another time.
I would try to change that reservation, or just cancel it. The information says that we need to be there at 9:30, and Ohana has a problem with getting behind (at least whenever I eat there). I wouldn't risk it.