I have to tell you . . . When I cruise in October, 2003, that was the most disorganization I ever saw in one place. As soon as I got in, there were too many people in line, so they handed us a number and said they would call. So, we waited. They called our number and we got the time / day that we wanted for dinner. Then, I asked about the brunch. He told me to stand in the next line -- at the END! Forget it. I said "If I had known there were 2 lines, I would have waited in the brunch line when I was waiting for my dinner number to be called." He just looked at me, but did take my brunch reservation at the right time I wanted.
So, moral .... ASK as soon as you get in the room how they are doing it. And, you may want to have more than one person with you -- one person to stand in the dinner line and one in the brunch line.
Seriously, they need a better system. With all the technology available, you would think they could book the dinner / brunch / high tea reservations just like a doctor bookings. There are plenty of software applicaitons available that enable multiple people booking multiple reservations at the same time.