Welcome! I understand about posting, believe me, I'm fairly new and I've posted in the wrong places. It's ok, there are a lot of threads to figure out which is the right one.
No longer have anyone to pack school lunches for, however, I will offer a suggestion that I use to do. Have your children help pack their lunch the night before. Give them options, give them three different main items to choose from and they select the rest with your guidance.
They are much more likely to eat the entire lunch if they had a hand in putting it together.
Also, and to this day my daughter still talks about this, when they go to bed, add a special note from you in their lunch bag. She would LOVE reading notes of encouragement at lunchtime, put a smile on her face. Such as, if they have a test that day, tell them they will do great and how proud you are of them. Even a Happy Face with a "I Love You! Hope you are having a great day!" Just knowing Mom did something special will brighten their day.