My parents and I have always stayed on the Atrium Club Level at the Contemporary and we have never tipped the Cast Members who work up there, because they are not allowed to accept money and if they do they can be fired. If they do something amaizing for us we always thank them since they are happy to help us.
That is true, they are not allowed. During our AKL concerige stay, a fellow guest tried to tip on the the men. He politely refused and was a bit embarresed.
It's true that you cannot tip with $$$ but if you do a search on this board (and it works) you will find that people who have gone in the past, receive exceptional service again before their next trip sometimes bring treats from their home locales to share with CMs (specialty candies etc.). You could also write a note praising the CM's service to his/her superior which often carries more weight (no pun intended) than any candy etc.