Can only offer what we did....
We took some of the following with us....and purchased the rest during our grocery stop at Publix....
We had a stryrofaom cooler for our room...(purchased at Publix for $3.99) and filled it with ice each day....had no problems whatsoever.
We had Pop-tarts, bagels, fresh fruit, cheese, chips/pretzels, dip, fresh veggies, etc....
Each morning we would take a Pop-tart, bagel (or two) to the food court....used their toaster and availed ourselves of butter, jelly, cream cheese, etc.....and filled our resort mugs with whatever....(note...probably the only suitable beverages for the mugs would be hot chocolate or hot tea....I had coffee....the mug refills do not include juice or milk)...
We ate our "essentially free" breakfast in the food courts....at nite...there were fresh fruits/veggies with dip, snacks, etc....
I also brought along a "hot-pot" from home along with some Ramen noodle mix...(kids love these)....and (after a couple of cool evenings at the parks....this was a welcome dinner/bedtime snack)....
You can also take munchies into the parks with you for in between meal snacking if necessary....not a word was ever said during our daily security screenings.....
Do purchase bottled water or cans of pop, etc...whatever your beverage of choice during your grocery stop....you will save $$$$...WDW serves Coke products only...and we are generally a Pepsi family.....NO GLASS BOTTLES please!!!
There's much more I'm probably leaving out....but you can definitely same money by bringing some of your own food items with you....
We found the Publix store to be very reasonably priced...........
Enjoy your trip
