I've started our Garden Grocer list for September also (glad to know I'm not the only one that plans that far ahead) and I've got a few snacks for late night snacking at the hotel (chips, salsa, hummus, etc) and snacks for the parks (granola bars, apples, nuts, carrots, pretzels) and then some breakfast food (bananas, cereal, yogurt). Something I learned on our last trip is to avoid easily crushed food, like crackers and goldfish, unless you can put them in a hard container like those take and toss snack containers or an empty pringles tube. we ate a lot of cheddar flavored dust last time we were there because our snacks got crushed in the backpack.
i also avoid a lot of sweet snacks because there are so many yummy desserts at WDW and I feel like we get way more sugar than we need from cupcakes and dole whips.