I know there are few people that are still packing kid lunches, but these could be helpful for anyone, I think. I pack everyone DS, DD and DH's lunch between q2 nebs overnight when I'm sick so I can focus on important things during the day, DSD mostly fends for herself with my help. I pack lunch boxes in one section black/clear lid food prep containers. My kids will eat typically warm foods cold and be happy about it.
DD (currently having tummy issues): Peach Greek yogurt, quarter of a grilled cheese, leftover french fries (yes, she is all about cold FFs), a few quartered grapes.
DS: Chipotle quesadillas (he will eat these cold) - leftover chipotle bowl mixture and cheese made into a quesadilla and sliced, half pickle, ritz sour cream and onion cracker chips, fresh strawberries.
DH: Cream cheese veggie wrap - chive and onion cream cheese spread on a tortilla, filled with spinach, thinly sliced carrot, broccoli, corn salad, chili lime shaved broccoli relish, green onion, red onion, cilantro and diced avocado. Pepper Jack cheese stick, whole pickle, craisins, grapes.