We always bring water bottles (with lots of ice) that we refill throughout the day and I bring some "kid snacks" - granola bars, fruit snacks, etc. for when they need something quick. We are local and eat breakfast at home (when. Go to WDW we usually eat in our room - oatmeal, yogurt, protein bars, fruit, etc.). We usually wind up with a mind afternoon meal and snacks (and sometimes gran fast food on the way home).
We've found some good (for Disney) prices at Downtown Disney. A few of the restaurants have happy hour - the other weekend we went to Catal and made a meal out of happy hour apps, and kids meals for the kids and DH and I each got a cocktail. It was probably like $60 for all of us, including drinks - not a huge meal (and one of my kiddos is only 2, so not eating a tom), but very nice and relaxing and not extremely expensive. The taquerilla at Tortilla Jo's also has good food at decent prices, and of course there's Earl of Sandwich. We like DTD as a nice break from the crowds midday and we've been pleased to find some nice, easy food options. Of course, going over to Harbor is also an option.
CS in the parks - I like Plaza Inn and the chicken dish is huge. Rancho del Zocalo also has decent portions and there are a lot of good options in DCA. I would just share when you can (we like to share an entree sometimes then splurge on a snack later in the day).