Welcome! I take my lunch every day to work (in a cooler also). Almost daily I will usually end up taking a boiled egg, sliced cheese, nuts, and SF jello...this gets me through breakfast, snacks, and a sweet treat. For lunch itself, I try to make leftovers at dinner the night before so I can have some kind of lean meat for lunch. If not, make him some tuna, salmon, or chicken salad. Or a regular salad is a possiblilty also. Just remember to send him a fork!
Hope this helps