First off, Weclome to Cruise Chat!
Next, what makes you think you will be eating with Retirees the whole time? It truly depends on what cruise line you sail on. Even then there are very few of them that are ALL old folks in a tub. We cruised for our Honeymoon and were with people our own age and every cruise since we were never "the kids" at the table. What cruise line are you thinking of using? When are you planning to do this (time of year can determine if family are on board.
I would say go for it. Even if you did end up with mostly older folks, you will still have a great time.
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