We did granola bars and juice in the room instead of wasting time waiting for food to come to a table. It was much more relaxing as people could get dressed while others were eating. Target and other stores are not far so if it was now, I'd probably grab yogurt also. When my kids were little, I gave each kid a plastic baggie with snacks (goldfish, cheese/crackers, etc). I agree with others that sodas can be a downfall of money and I've learned to drink water and only have a soda when it comes with the meal.
My biggest and always downfall was I wouldn't budget treats into my budget. We'd get there and their bakery, dole whips, etc just call you. I've learned to now put at least one treat into the budget every day. (if not two LOL).
Plaza Inn you could buy two dinners and split with your kids. Same with the Mexican place in Frontierland (I can never remember the name). The little red wagon with the corn dogs have the meal price but you can just get the corn dog without the bag of chips and soda. The bakeries will cut a cupcake in half for you if you ask.
If you get the soup in a bread bowl in DCA, ask for the bread in a bag and snack on it later. We found that when we went back to our room at lunchtime, there were coupons for discounted pizza. I think you said it closed early one night, I would be tempted to go to Dennys as it was around the same price as other Dennys. As someone else said, IHOP was more expensive than any I've ever been to. McDonalds seemed to have higher prices than normal McD's but still cheaper than a sit down.
Someone help me with the name of the sub place in DTD. ???? We don't have one here so the only time I've been there is when we went to DL. I joined their club a few weeks before we went and got certificates for a free sandwich. It only lasts for so long so you need to do it right before you go. I also joined the Jamba Juice and got a coupon for that.
Souvenirs. I love the idea of waiting until the end. Since my kids are adults now, I'm not up on what kids are buying. If you are considering a souvenir for you, my favorite was a $10 picture frame with the year that I put a photo of all of us in. It reminds me of the trip every time I look at it. Some have gone to
Walmart or Target and got some Disney stuff to do on the car ride to/from DL.