The first thing that you need to consider when building a survival box is your nutritional goals. Each member of the family has its own nutritional need, so you must pack foods that contain varying amounts of calories, fiber, vitamin A, iron, protein, vitamin C and carbohydrates.
Your children should get enough fiber, however you need to make sure that they will not overfill it before they get enough nutrients and calories. Daily intake of 10g of fiber is recommended for kids. You can get these vitamins and nutrients in fruits and vegetables.
As mentioned earlier, it is best to pack dried fruits and vegetables since they are more compact. In building your survival box, you need to think about what your family will want to eat. If your family prefers to eat dried veggies in a soup or stew, include that in your box.