Moms with school aged kiddos, I need your lunch prep hacks! :)

So I'm about to start helping my SO with packing lunchboxes for his 5 year old and 12 year old, rather than them always getting cafeteria lunch at school. So my mamas, please share your best shopping, prep, and general kid lunch preps with me. I know how mine were packed each day but I've never been the one making the grocery list for the items, and since we will buy in bulk, I just wanna strategize the best way possible in doing so. Thanks in advance 😁😁