Thanks to John for writing the post and getting it to us so quickly.
Below are some proposed social media messages. Please tweak as needed.
Twitter (@wikimedia/@wikipedia):
• The Wikidata:Menu Challenge starts now. Translate labels and take photos of food. Let's make #tastydata!
Facebook/Google+:
• The Wikidata:Menu Challenge starts now. Translate labels both in text and the audio of the pronunciation and take photos of food. Let's make #tastydata!