I second Whitewater in the GCH (if you are somewhere in DCA and it's convenient...) it was cheap, quiet, and a very nice break. It's a hidden gem for sure. Modified counter service, some items you can grab and go (salads, sandwiches, desserts, etc), or order at the cashier (burgers, chicken sandwiches, nachos, etc) and the staff will give you a number and bring the food right to your table. There is indoor and outdoor seating there (and a number of cute wild cats to see!). And, I found out, one of the only places anywhere in DLR where you can get free pop refills! If you don't stay at the DLR hotels you can't get back INTO the park the way you get out of it, but for us it was okay because the plan was to shop in DTD afterward. The exit from DCA into GCH is right by the Whitewater Snacks. You just go through the tunnel and make a quick left.
I like Stage Door snacks in Frontierland...it's off to and almost behind the Golden Horseshoe. We ate there twice actually, both times with NO line. Compare that to the long lines at the Hungry Bear and it's worth it even though the menu is limited. I got chicken strips both days, but they were big meaty ones. You could get apples or french fries with and sit on the shared patio by the other cafes along ROM. My kids were totally satisfied with it especially considering the lack of line. My husband and I shared the chicken strips, it's a pretty big portion.