Hi! Thanks to the Dis I had heard about Picnic in the Park before going to WDW this past Easter. The Picnic in the Park was offered however, I had to ask 2 CMs before they were able to tell me where to find it!
It ended up being offered at the (I think) Island Mercantile. It was all grab and go food. You had to grab a reusable shopping bag and fill it according to the posted guide. We did the picnic for 2 and we were able to choose 2 sandwiches (from the pre-made sammies in the fridge - which were so yummy!), 2 bags of chips, 2 bottles of water, and 2 desserts (apple, orange, banana, cookie, rice krispie treat). It was $17.99ish.
I thought it was one of the best deals in the park! The sandwiches were not the typical turkey/ham/roast beef sammies... we had some really interesting sammies!