My solution to kids constantly raiding the snack cupboard! I also had several cereals that my kids were tired of. Add chocolate chips, marshmallows, and nuts and its a whole new snack!
the cereals I used were - Chex, golden grahams, cheerios. The kids each have a small container with their name, and they have to stay out of the cupboards!! or ELSE!! I have another list of things they can choose from - yogurt, string cheese, a fruit snack, and an apple. Some days it works, some days I have to remind them or get after them for sneaking stuff.