Lots of ways to save:
Bring breakfast and some snack items with you, also those cups of mac & cheese, or ramen noodles, or cup o'soup with crackers. The kids would be so hungry when we would return to the room so it was comfort food, plus filled them up. While not the most nutritious, your on vacation so for us we would let it slide.
I would order water from Staples and have delivered to the resort, huge saving here, water gets costly very quickly.
There is Garden Grocer which you could order and have delivered. But be careful not to over order, so that nothing goes to waste.
Most restaurant's will let you share, some will give you the plate to split and other will do it in the kitchen for you. But do ask before ordering, and make sure to tip for 2 people.
Check out the appetizer platters, most TS have something like this, if not quite enough add in a side salad to share as well.... or dessert..
Walk around the World Showcase in Epcot, lots of kiosks to grab something, eggrolls in China, crepes in France you get the idea.
Take a look at the menus here, and the food pictures to get a idea and over on allears they have complete menus with pricing..
Have a magical time...