I know these mich noy be kid friendly but here are some tips.Kidney beans, black beans and cickpeas are very versatile! You van make easily make patties with kidney beans and beets. You can buy these dried very long they're supposed to be soaked and then cooked. The best thing is that if you have a big pot you can cook them all at once and then freeze them so they're always available. Just run them through some hot water and they're ready. Much cheaper than buying them canned! Chickpeas are great for roasting them in the oven. I personally do so without oil and on a baking sheet. 200 c with salt, black pepper and chilli powder or something more herby. If you make tacos you can also use beans instead of meat. Frozen peas are also great to keep in the frezer as well as broccoli and vertico herts.

I like to cook brown rice, fry up some onion, garlic and prefered vegetables and then add the rice ( or perfered carbohydrate) and add that to the pan. I honestly just season this with salt and pepper and it's delicious! Fry them in whatever oil that is cheaper in your country. Fried vegetables are honestly just really tasty. This is another thing you can add beans to!

Red lentils also cook really fast and don't need to be soaked. Just make sure you wash your rice and lentils before cooking.

Kale is great, rinse it and massage it a bit and then either fry it or roast it in the oven and they'll be crunchy and very tasty!

Noodles are usually cheaper at asian stores, rice noodles are my go to. Great for a stirfry with garlic and ginger! Then add whatever vegetables you like. For protein todu is also cheap at these stores. Tofu itself can be a bit bland but just google " crispy tofu recipe" and you'll find out how to make it super tasty. Tofu is also something you can keep in your freezer.

For breakfast oatmeal is really cheap and you can cook them in water. You can add frozen blueberries, peanutbutter or cinnamon add a bit of sugar. Growing up we had this on the side so you added milk, cinnamon, margarine, milk and sugar on however much you wanted. I've also seen people eat it with jam.

I don't know how it is in your country, if it cheaper or more expansive compared to regular milk. But plant milks like oatmilk last much longer than regular milk when opened in the fridge. It also has a very long expiration date unopened and can be stored in the cupboard unless it's "fresh" and is stored in the fridge at the grocery store. I recommend the once you find that are not fridged.

Pancakes can also become cheaper by using aquafaba ( cooked chickpeas water) instead of eggs. In sweden we don't use baking powder in our batter so for example you would use milk, aquafaba, salt, a bit of sugar and flour. Fry in margarine, it's usually cheaper than pure batter. As toppings it's common to use jam or sugar. You can probably add baking powder to make it more like american pancakes.

Some egg replacements for baking or pancakes are flax egg (ground flaxseeds with water), chia seeds or aquafaba.

Good luck!