I got this from the Mousesavers newsletter:
The offer is available for the following date ranges:
8/28/15 – 10/2/15
10/25/15 – 10/31/15
11/8/15 – 11/19/15
12/15/15 – 12/21/15
You must check in during above date, stay at least 3 nights and get at least 2-day tickets with either Park Hopper or Water Park Fun & More (or both) in order to qualify for Free Dining. Certain resorts and room types are excluded from the offer.
Here's the full link.