I don't have kids, but cook every night (while working 70 hours/week).
Some stuff I keep on hand that helps.
Beans and rice. You got beans and rice, you've always got a meal (as I found out while trying to close on a house a few months back. We had pinto beans in some form everyday for 3 straight weeks. we put on a food cost clinic that month with the mortgage lady wanting bank statements every week). You make a pot of pintos once or twice a week, and there's just so much you can do with them. Beans/rice, of course, but then there's bean burritos/quesadillas. Beans/rice with over easy eggs on top is also phenomenal. I've actually never had much luck with beans in a slow-cooker (I kind of hate slow cookers in general). I find letting them soak for a long time (overnight to 24 hours) with a bit of kosher salt helps them cook very quickly (can be done in 1.5-hours in a dutch oven). I go ahead and put them on the stove with just water, then add the other ingredients and seasoning as they cook. To keep it interesting, just vary the protein you throw in with them. I do alot different sausage with them, from Jimmy Dean type to chorizo.
And get a rice cooker (along with 25 lb bags of Jasmine or Basmati from Costco/Sam's, white rice is okay, but Jasmine/Basmati are so much better). A rice cooker will fire out perfect rice every time, and more importantly, with virtually none of your attention. Again, when you've got great, hassle free rice, you are well on the way to a full meal.
Flank steak. It's the protein I buy most often. It's so delicious, quick, and versatile. And very cost effective for feeding a bunch of people. From flank steak tacos to serving it over rice with some sauteed veggies to just serving it on a nice salad.
Similarly, boneless chicken thighs are great for most of the same applications. I really don't like chicken breasts, and don't think I've bought them years.
Speaking of salads. Grocery stores with salad bars or a good selection of pre-made boxed or bagged salads are great. Salad bars are best, but the pre-mades have a come a long way over the last few years. It may not seem cost effective, but they are well worth it for the time savings. Many nights, dinner is whatever meat I feel like throwing on the grill on top of a salad.
Of course, always have tortillas on hand. They last forever, and always seem to come in handy when whipping something together.
I pretty much always have some chuck roast in the freezer for a Sunday beef stew or Smail's chili to last into the week.
One random suggestion is the
frozen philly meat from Sam's/Costco . In the freezer, so always on hand. Comes out great with grilled peppers/onions/mushrooms to throw in a burrito/quesadilla or to just serve over rice.