Well if its culinary that he is interested in, you should do the Chef's Table. I think it is less expensive and the Chef prepares a special meal for you. I also think he discussed the galley and how it is run.
The Behind the Scenes tour does more than the galley, it also does the engineering and theater areas.
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
NCL Dream October 2006, RCCL Mariner OTS June 2007