Have you considered buying one there, then just leaving it? It could be worth the money, depending on what you save.
That's what we did on our first trip to Hawaii 2 years ago. We stayed at the Hilton Waikoloa Village on Hilton Honors points, but just to eat there was costing us more than the room would have! We bought a small microwave from
Walmart (they're everywhere!) along with some simple foods to heat up, etc., got a small, cube-type fridge for free from the hotel. We just left the microwave behind, it cost about $40, saved that on one meal. The HWV is huge, you walk miles just to get out of the place, and kids always get hungry in the middle of the night!
If you're flying to WDW and won't have a rent car, you can order groceries delivered from
www.wegoshop.com Their prices are quite reasonable for the service, and they can buy just about anything, you can even specify the store. You could have them pick up a small microwave, some foodstuff for the room (don't forget paper plates, forks, etc), then either rent a fridge from the hotel, or you could have wegoshop pick you up a styrofoam cooler at Walmart, then just leave it behind as well.
I think you're smart to try to plan some meals in room. Not anything elaborate, just simple things like sandwiches, soup, hot dogs, maybe frozen dinners, breakfast stuff, etc. True, you will be doing most of your eating while out of the room, but you need to be preapred for the kid who gets the hungries in the middle of the night and the eateries are either closed or a long hike away.