Yes, they have a welcome aboard parade the first night on the Voyager class ships (and the Freedom class too). I have not been on RCI cruise for a while so I can't answer you buffet question for sure unless you are referring to an every night midnight buffet. Most of the lines (ok, all the ones I have sailed on) no longer do a nightly midnight buffet. This is due to the fact that most of the ships have some form of 24 hr food service (pizza, deli, grill etc) and they don't need another form of food service. However, they typically have a "gala buffet" once in a cruise. If that is what you are referring to, I believe they still do some form of that.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise, Magic 1/14, Freedom x 2 6/14
NCL Dream October 2006, RCCL Mariner OTS June 2007, Celebrity Silhouette 2013