We always use paper plates and bowls to keep washing-up to a minimum. Anything in a tin is good. Pasta and a jar of sauce. Those flavoured rice packets that you add water to. Rice pudding, bit of cereal in a bag and carton of long-life milk (stays fresh quite a while even when opened). Don't forget a tin opener!
If it were me I'd take something like ham, egg or cheese sandwiches for lunch, something like homemade stew for evening meal that you can heat up on a camping stove
And some cereal and milk for breakfast!
Either that or bring a disposable barbecue and do burgers