Is that diet OK for growing kids or just adults?
More variety in your diet is likely to always be superior to less. That goes for both kids and adults. The trouble with younger kids is that deficiencies can impact their development and have more severe long term consequences, and they’re also less capable of seeking out foods to fill that gap.
My mom basically starved so we could eat. I remember her giving me her food regularly. I Still only ate once a day even with her sacrifices. I expect I will be doing the same at this rate so I wanna do more for them if I cam.
If the option is you all not eating enough, and eating primarily cheap bulk foods, do pick the cheap bulk foods. With cheap seasonings and making your own tortillas, breads, and gravies, you can have a large variety using the same 20ish cheap base ingredients.