Have recently started doing these for my kids (7 and 10) more consistently, as school meals are getting pricier and no longer fill them up anyway.
I usually have ham/cheese/roast chicken/tuna so can normally easily make barm cakes/wraps, and always include either chopped fruit in a tub or e.g. satsuma and apple. Sometimes I add a yoghurt or Babybel for more protein, and maybe a choc bar or cereal bar occasionally (nut-free school though), but what's good for bulking it out a bit? I sometimes do hummus and carrot sticks but it's usually extra savoury stuff I struggle with. I've offered cold omelettes but that's not been well received...if we have pasta leftovers such as pesto salad then I send that in but I don't want to be boiling pasta just for that. Sometimes I send a boiled egg but they complain about the smell...am I missing a trick here?! What else works well?
In winter I can do the two of them hot soup or pasta and send it in food flasks but I just feel like they need a bit more bulk at the moment. I sent a mixed salad today (tabbouleh/potato salad/random fridge veggie leftovers plus pot of dressing) today so will see how that went down. Maybe I just start sending two filled barms?!