At Disneyland, we think the best value (decent tasting, filling) meal is the pasta at Pizza Port. I love the chicken fusilli, and it's $9.49, and enough for two people.
We ate lunch at Blue Bayou last time; I'd give it a miss except for just dessert. I love good food, but this was pretty mediocre and expensive. You're paying for the setting. Go just for dessert and enjoy the experience with minimal cost.
The skewers at Bengal barbecue are a decent price, though not very large. Folks rave about the bacon wrapped asparagus.
Loaded baked potato soup at Carnation Cafe! $8.49 for a bowl, which is a pretty ridiculous price when you think about it, but nothing is cheap at Disney and this is delicious and filling.
Not sure about DCA, as I think the menu offerings have changed a lot since we were last there, two years ago. We are always a fan of the turkey legs

. Like everything, they are really climbing in price ($8.99) but you can feed at least two with one; and I'm always happy to get a big dose of protein in the kids while in the parks, to keep 'em from crashing.
The bread bowl soups at Pacific Wharf Cafe aren't fabulous, but they are decent and good-sized portions. I liked the corn chowder the best.
In DTD, I thought Brennan's was pretty good, and had a fun atmosphere. Rainforest Cafe is really overpriced, but fun if you haven't done it before (we don't have one locally, so it's a treat for our kids). I would just get an order of the their nachos and maybe a salad or two to share.