An ideal lunchbox for a child will contain real food without the grains when possible.
So a combination of a good protein source like good quality ham, hard boiled egg or greek yoghurt with seeds added, a good healthy fat source like cheddar cheese or olives and some low carb veggies, like cucumber, and cherry tomatoes. Any by the way no juices, whole milk or water are the best options.
So get plan to get rid of the sliced pan, cheese strings and super sweetened yoghurt sticks. Food for thought!