Then why don't you just dish small helpings of the protein component (to prevent it being hugely expensive) and put the rest in serving dishes so that the children can help themselves, and all leftovers are the unused sort that can be recycled into another dinner?
Weigh rice/pasta etc before cooking so you aren't cooking way too much and causing waste.
Definitely plan your meals, or at least always have in mind the items that NEED to be used in the next day or two. eg, in addition to stuff in better nick, right now I have a swede going a bit soft so that is a priority, an open half tin of coconut milk so that needs to be used in the next couple of days. I know I have a ropey leek and a LOT of cabbage. So I have a loose plan in my head - root veg & barley stew using some homemade stock from the freezer. Stirfry cabbage as a side veg to every meal, with appropriate spicings if wanted. Veg, lentil & coconut soup for a lunch, or possibly a coconut based vegetable curry for a dinner.
Thinking like this saves waste for us.
Don't shop until you HAVE to. Look in your fridge/cupboard/freezer. You'll be surprised what you can make, and probably how much food you have if you are anything like me.
Just accept that cheaper fruit and veg is fine, and ditch any of the pricey stuff. We currently have lots of onions, carrots, cabbages, spring greens, swede & squash (were in the Aldi super 6 recently), pulses, frozen peas, broad beans, green beans, spinach, tinned tomatoes for veg and apples, oranges, bananas and blackberries we froze in the autumn for fruit. Occasionally some cheap tinned peaches. It's fine, and plenty of dietary variety. For now, peppers, courgettes, aubergines, mangetout, berries, soft fruits are not on the menu here unless reduced to clear.
You can stretch mince dishes a long way with lots of finely grated carrot and a generous handful of oats (keep an eye on water requirements). I was truly amazed at how it all swelled and got an extra lunch helping for me and my 2 year old from our normal batch.
Know the price of your staples so you know a good deal when you see one, and can buy it, but don't get lured in by advertising.
Do things like cut up sausages in toad in the hole/sausage casserole, they go further, you can use less.
Use highly flavoured meats like bacon/chorizo and a little goes a long way.
Save meat bones, and brew them up with a tired onion/carrot to make stock. It's so good for you and so delicious. Just add root veg & dark lentils/pearl barley for a really great chunky stew, or use it to make a risotto.
Have a jacket potatoes night, a something on toast night, a soup & a crumble night and/or a eggs, wedges & beans night or similar each week to keep costs down.
CHeck out A girl called Jack's website, lots of very cheap meal ideas, you could see if there's anything you could try on your family.
It's also the perfect time of year to try some growing your own if that might work for you? I always get a very good return on french beans & courgettes especially. Also lettucey type bits very worthwhile growing - you can do those in icecream tubs on a windowsill.