My son had braces only on the front and with bread as long as it is not extremely crunchy like biscotti crunchy he did not break anything. As for what to pack,
cut up apples
grapes
watermelon
strawberries
any type of fruit cup
dry cereal (my kids love munching on mini wheats)
you could put the chips in the lunch box but smash them before putting them in so they are already broken up
It seems like there is so much that they can not have but as long as they are careful and you keep up on what they can and cannot have he will make it. My son had top and bottom with just the front teeth for 10 months and has had a retainer for the last 4 months. The retainer is more of the pain then the braces themselves and he was about the same age that your son is when he got them.