Here are some ideas for you to consider. There are some wonderful inventions out there.
There are holders for salads that also have separate space for dips.
They have holders for cereal, etc., with space to keep milk separate.
They have "thermoses" that you can store two different foods in. For instance, the top will keep soup hot while the bottom keeps salad cold. Any hot and cold foods can be used. You can even put soups or lasagna in the hot part. Anything that needs to stay hot and cold.
I would do some things once a week (to keep them fresh), others every couple of weeks. Here are some ideas for things to prepare in advance to grab quickly:
crackers, maybe even with peanut butter
cut up carrots/celery/melons/berries
salads
You can also keep these things in stock. Individual servings of:
fruit, canned or fresh
string cheese
yogurt
nuts
granola
granola bars
some things to make
sandwiches (choose from any of these)
turkey, chicken, ham, roast beef (not necessarily sliced, from your own cooking as well)
an assortment of pickles and vegetables
cheeses
you can also send things like:
pasta and sauce - hot
lasagne - hot
soup/stew - hot
shephard's pie - hot - simply mashed potato with choice of meat and veggies - it is a casserole
pinwheel sandwiches - flour tortillas with your choice of toppings - rolled up and sliced round
cold pizza slices
mac and cheese with choice of veggies and meats - hot
muffins/breads - homemade or not - oatmeal, zucchini, carrot, apple, banana, chocolate chip
homemade fruit leather
dried fruits
homemade trail mix
For cold lunches, I would consider keeping and ice pack in the luch boxes. Not if there will be foods that need to stay hot.
Also, milk and water are the best drink choices, but a 100% juice will not hurt every once in a while.
Hope this helps somewhat.
S.