If you're Alliance, the brand-new quest series starts with Children's Week, offered by Orphan Matron Nightingale in Stormwind; if you're Horde, it starts with Children's Week, offered by Orphan Matron Battlewail in Orgrimmar. Both new quest lines will see you surveying the changes to the local landscape in Cataclysm, in addition to meeting important lore figures and paying your respects to the dead. Afterwards, you'll go out for the traditional ice cream treat and then visit a local vendor to get kites to fly. Wowhead News has more details on the individual quests if you don't mind spoiling yourself.
The quest lines end with the offer of a new noncombat pet in addition to the usual Piglet's Collar, Rat Cage, and Turtle Box -- a new Snail's Shell! It looks like the Outland quest series will also offer a new pet called Legs, though there don't appear to be any new quests there. Experienced orphan herders thus have a reason to pick up a tyke again this year, and with any luck, the Wrath of the Lich King variant will be available even if you've done it before.