We've sailed in a cat 3 on 4 of the 5 (soon to be 5 out of 6)
DCL cruises we've been on and our experiences have been......
We have requested a dining rotation on 2 of the 4 and did not receive it either time. Since they recently started using a land-based concierge, we have requested a rotation for our cruise next month, through her, but we'll have to wait to see if we get it. A few months prior to your cruise, you will receive the email address for the land-based concierge.
On our first 2 cat 3 cruises, the room was stocked with 6 cans of soda, but was not restocked. On the last 2 cat 3 cruises, the room was stocked with six bottles of bottled water, and not restocked. We have always received a plate of "goodies" every day and had a bowl of fruit in the room when we boarded.
You can order a hot breakfast, except on the last morning (you can order continental that morning - order it the night before). You can also order room service dinner from the regular dining room menu. Cats 1 and 2 can order room service from Palo.
On the EB repo in 2005, our DS received a few arcade cards and they decorated our cabin door on my birthday (and gave me a lithograph as a birthday present).
I would definitely advise going to the Concierge meeting when you board and they will do their best to get you any Palo or spa ressies you want. One of the times that we did not get our requested dining rotation, they went to the dining manager and got it changed while we relaxed with a cup of coffee and cookies.
If you have kids in either the Lab or the Club, they will register them and give you your pager at the Concierge meeting - no need to do anything in the terminal or go to the Lab/Club.
Hmmmm... if I think of anything else, I'll pop back onto this thread and post again.