Keep checking online even while you are at WDW because something might open up. I have picked up an ADR that I had been trying to pick up for over a month online the night before we wanted to eat at the restaurant as we were sitting at the bus stop of our resort waiting for a bus to take us to DTD.
It never hurts to walk up and ask, the most they can do is say no (which we saw a lot of last week when we were at WDW). I would recommend trying to go right when the place opens or at off times for your best chance.
If all else fails, we hit some surprisingly good counter service this time. BOG at MK was amazing for lunch. It is a must do in my opinion. The line may look horrible, but ask because what looked like over an hour long line to me was only 15 minutes. If you like salads, we ate at the ABC Commissary for the first time the last trip and the Asian Chicken salad was really good. DH said the couscous salad was really good too. They have a holiday gingerbread cupcake there right now that was great too. I had always heard the commissary wasn't very good, but we really liked it.