We vacation a lot about 4 weeks a year but not all at Disney. However, they are all in timeshares. At Disney we tend to eat out more than other vacations.
For Disney, we usually go about 10 plus days since we are traveling from the West Coast. I'll usually plan 2 to 3 breakfasts out and then, the rest in. I do notice that my family is more hungry in the morning so, I tend to more hearty breakfasts. I try and make sure our meals can used on more than one meal. For example, if I buy sour dough bread, I'll make grilled cheese with it and then, if we have leftovers at the end of the trip I'll make either french toast or french toast cassorole in the oven. Other good breakfast items are plain bagel sandwich with bacon or ham with eggs and cheese. My family also likes plain bagel with cream cheese and salami for lunch/dinner. Or if I buy tortillas I'll buy enought to make quesdillas for lunch, egg/bacon burritos for breakfast and chicken tacos for dinner. One of my favorite things to do on our other vacations is to shop at Costco and buy either marinated tri-tip or turkey breast (depends on the season as some of this stuff is seasonal), mashed potatoes or scalloped potatoes, steamed carrots for dinner. If it is near Thanksgiving time I'll get cranberry sauce, stuffing, gravy, etc.. We'll use the leftover meat for sandwiches all week. Then, I'll also buy hummus to eat the leftover carrots with. But we generally don't shop at Costco at WDW but I do on my other timeshare vacations. I generally don't buy too many snacks for Disney world because you are eating so much as it is that the snacks go to waste except I will buy fruit as we rarely order that with meals. I'll buy yogurt and granola bars so, we could have that breakfast knowing we can take the granola home on the plane ride. Last time we were at WDW for 15 days but 5 days were on cruise. Anyways, I ordered 3 cases of water and we went through all of it but it was June. You can freeze water bottles to use as for ice in your lunch sack. So, you can add grapes and other fruit and keep it cool. I've even froze grapes. Makes a great snack. If I was only going for a short trip like 4 or 5 days I would really not order much except breakfast and water. We are kinda of lucky to be able to order food for longer trip. On average we spend about $150 on groceries just for breakfast, sandwiches, fruit and waters.
My other vacations I have list of easy items to make like marinated beef fajitas, marinated chicken tacos, shepherd's pie, Lasagna (homemade), spaghetti, fish (if we are in Hawaii---we will grill this daily), steaks with grilled shrimp, etc... I get a lot of recipes from Rachel Ray as her meals are delicous and quick and don't taste like frozen or out of box.
Good luck...
Bill 
