If you want to check to see if any ADR's are still available for your trip, call Disney Dining. I highly recommend having a few -- you mentioned the Blue Bayou . . . also Carnation Cafe is great for lunch (I had a turkey sandwich on pretzel bread, DH had the chicken club crossiant -- they also have pot roast sandwiches, pot pie, caesar salad, etc) and also Cafe Orleans (DH and I split the Monte Cristo sandwich -- also have gumbo, salads, other sandwiches). Those are my 2 favorite places for lunch that accept ADR's.
We loved the place in Adventureland that sells tons of fruit boxes and veggie/dip boxes -- very good and healthy.
Someone already suggested the Pizza Port -- the potions are "ginormous". I got the pasta with the pesto-alfredo sauce and chicken -- *very* rich and so big that I made DH split it with me. The salads looked great too.
We also like the Pier over at DCA (if you're going there) that sells soups and salads in sourdough breadbowls -- good.
DH loves the Stagedoor cafe over by Thunder Mtn. RR -- chickenstrips, fries, mozarella strips.
Also, the Plaza Inn has yummy food as well. Happy dining!

oops, I just realized that you said you'll just be there for a Sunday -- probably gave you a few too many options LOL!!