It was on the Magic. We had main dining so didn't see how it worked, but I was told that counselors waited at the front of each restaurant and kids who wanted to go were checked in there by their parents at 9:00 p.m.. It was listed in the Navigator with how to do it.
We are wait listed for main (that's what happens when you book 6 weeks out lol) of our 13 cruises, we had late once and honestly we hated it. I am accepting that I will probably have late this time and am going to avoid thinking about it until I have to. We just don't like eating that late. I will wish for some pixie dust and anything is possible

Funny, some love late, some love main. Thank goodness not everyone wants the same thing.
My kids agree that it seems the most fun activities occur during late dining time and with so many kids main is the only thing that works for us. Even though a little rushed getting ready, better than sleeping in their soup bowl.
By the time we receive entrees, my kids have devoured their mickey bars and are off to the club/lab til show time. My kids don't spend much time in the club or lab, but when they do it is usually while we finish dinner. Big ones take the littler ones and they take turns so we actually each only do it once a cruise.
We had rooms that were not close together on our cruise last week and it was a pain but doable and considering the great rates we paid I was ok with the inconvenience. We were on the same deck, same side, but opposite ends. It would actually have been closer and faster to have been on different decks above or below each other near the stairs. We had one cruise where our rooms were separated by one cabin. We have also cruised and gotten people to switch with us to put our rooms together after boarding the ship.
Our best upgrade was booking connecting 10s. When our luggage tags came, they were for side by side 8s. We got called and told to change room numbers on luggage tags and had been complimentary upgraded to connecting 6s. At port we then paid to upgrade to a 3 and 4 connecting at last minute. Upgrade cost about 2k. All total the cruise was around 6k with the upgrade. Now that was a nice price and probably never happen again, it was I think an October cruise
This time we just decided we need connecting rooms for sure and booked two connecting 4s.
I am getting excited even though we just got off the ship