I honestly don't think anything they did would top the unholy merging of two of the most known burgers in the world. The kind of news that would generate would bring peak awareness and having it in a single day store where it's practically exclusive and limited run is sure to have people a-buzz. Just think Willy Wonka and the Golden Ticket. The thing you would have to make sure is promote that this is in honor of Peace One Day.
If the CEO though he could do better, why hasn't he.
He said McDonalds and Burger King can do better to raise awareness to the real issue than a market gimmick and he is right, even distributing leaflets about conflicts around the globe and on how the first world governments don't even pretend to do something about them in every McDonald's and Burger King for a month would do way more than this, bonus points if they included photos. But they won't do this because this can make them lose costumers, piss off governments and probably cost more money.