I don't have children yet (B day October) but send husband to work with:
sugar free jellies with fresh fruit set into it. You could make this with different colour jelly (letting each one set before adding another) for kids. My mum used to do this.
tortilla wrpas with cream cheese, turkey meat and lettuce.
American style pastrami sandwich/bagel with mustard and lots of salad.
Carrot sticks with either a home made mackerel pate or houmous dip.
A bag of unsalted nuts.
Pasta salad usually left over from the night before, with caramelised onions, peppers etc and pesto mixed in. Same goes for cous cous or quinoa.
Home made carrot cake. I make a tray bake and cut into pieces then freeze. The piece defrosts by lunch time and keeps the lunch box cool.
Natural yoghurt with some frozen fruit dropped in, again keeps the yoghurt cool for lunch time and sweetens it slightly. Might add honey too if using figs and almonds as the fruit.
A piece of cheese with a tomato and a little pack of oatcakes - to make his own end of lunch cheese course.
A piece of fruit or a fruit salad, all covered in lemon juice to stop it going brown.
Of course when baby arrives husband might have to make his own lunch so will revert back to ham sandwiches and a apple. Until then he is super healthy.
Hope this is helpful.