I am in the same boat - DDs are 1.5 and 3.5.
Monthly online shops. I buy two large chickens, roast them and bag the meat into portions (4-5 depending on how large the chickens are). I buy three large packs of minced meat (750g) and do a big batch cook of spag bol mix and freeze it in portions - usually I get 5 portions from this, and then add mash to make cottage pie, or add chilli and cumin and coriander and kidney beans to make chilli, to vary things up. I shove loads of veg in it. I buy lots of top-quality sausages and Tesco finest fish fingers, and loads of frozen veg of different varieties. Also tinned tomatoes, loads of eggs, roasted peppers in jars, tinned peaches, custard, butternut squashes (they keep really well and you can roast them for pasta, risotto, or soup), as much milk and bread as the freezer will hold. Loads of pasta, rice and couscous. Also red lentils - many is the time I eek out some leftover spag bol by adding lentils to the mix. I also make a mean lentil and chickpea curry which is cheap as chips, so I keep tins of chickpeas in too. Ham, cheese, washing powder, cleaning stuff, nappies etc all go into the shop for the whole month. Then I buy one week's worth of fresh salad and veg and draw out £100 I keep in the kitchen for grocery top ups. Freezer food and tins are the key!
From this I can make 5-8 minced meat meals (using the lentil trick), four chicken meals (fajitas, chicken noodle soup, chicken and broccoli pasta bake using the frozen veg and adding mustard, creme fraiche and cheese, chicken curry, etc etc). I make sausage pasta dishes, roast sausages with peppers and squash and chickpeas, or have sausage and mash (usually all three in any given month), and we eat a lot of fish finger sandwiches with peas and sweetcorn. Also a lot of omelettes and salad, scrambled egg and beans on toast (cheap and nutritious!), a lot of pasta dishes and risottos with whatever I have to hand, as well as the chickpea and lentil curry. The roasted peppers work really well for pasta dishes. We also have a bits and pieces night every now and again, where we raid whatever's left and make a random meal from it. I take leftovers for lunch.
My monthly shop is about £160, plus £100 for extra groceries, and that includes cleaning products, toiletries, and nappies. On a bad month where everything has run out it'll be about £300 for the whole month. I think that's pretty good going.