Thankfully we don't have to worry too much about money, but I meal plan and shop online as its the only way I don't go off the rails- I also grew up very poor and think it still affects me now. Family of 3 and spend £400 a month including top up shops. Planning goes a long way to be honest.
I buy some things in bulk: hand-wash, shower gel, toothpaste, dairy alternative milk etc (but have to check it actually works out cheaper as it doesn't always), that saves a fair bit. I buy the biggest pack of chicken breasts for example and decant them into freezer bags to pop in the freezer, this saves a fair few £ per kg and isn't much more effort; also do this for mince, sausages etc.
Buy some stuff seasonally, berries during winter for example and so expensive and not usually that good quality- so buy more pears etc and then buy them in the summer, do get frozen berries in winter sometimes though.
Plan meals around what's on offer and snacks. DS likes cheesestrings and babybels for example, one is usually on offer so I'll just buy whichever is- of course appreciate this isn't always possible for children who need the same brand all of the time etc.
I get cash out at the start of the month for top up shops, we don't go without so if I run out of cash I'll get it on my card, but it's so easy to lose track of those small shops and just popping in for one or two things.
Essentially though as long as you can afford it then it doesn't matter what you spend, there are ways to cut down though if you need to. The different lunches sound lovely as do the Snacks but no wonder you're spending loads!