Breakfast in room, cereal, milk, fruit, instant oatmeal, pop tarts, breakfast bars. My friends bring bagels and bread from home and toast them in the food court, they bring their own cream cheese. I have made muffins, brownies and cookies and brought them with us. I use a plastic shoes box, and pad it with wax paper and baggies with air in them, really helps protect them, a suggestion from another friend is to use rubber bands to keep the lid shut tight.
Take snacks into the parks, granola, cereal bars, apples, crackers, or those little can of Pringles, or those cans of Doritos, just nothing that melts. Water and drinks are another way to save, bring them with you, or order from somewhere like garden grocer.
Sharing meals - lots of QS meal that can be shared - maybe 3 adult meal between the 4 of you would be a savings. Or even 2 adult meals if your girls aren't big eater, which you could use the savings for Mickey bars later on.
Most restaurant will let you share TS meals, Tutto pasta is wonderful and huge portion. Via Napoli you could share a pizza. Tell them you want to share most will divide for you some will give you the plate so you can do it yourself.
Appetizer night, When our girls were this age we could get a large family appetizer and 2 side salads, and it was more than enough food to share, Rainforest, Planet Hollywood, and T-Rex, have the best ones with the most choices ( for what my family likes). You could even get one dessert to share with the 4 of you, or head to Ghirardelli's and share the large ice cream sundae.
Take some time, to check out menus so that you have a idea of what is offered.
Have a great trip...