Use a slow cooker or pressure cooker to batch cook, you can start it off at a quiet moment/nap time. Or do easy stuff like jacket potatoes. Don't make life hard on yourself. You can stick with some processed things for ease (sausages, fish fingers etc) but have more veg on the side. Frozen peas and sweetcorn are cheap and easy, quick-cooking stuff like mange tout.
Find ways to get your toddler involved - mine used to love washing/scrubbing carrots or potatoes in a bowl of water (even if we weren't having them that day, no harm in washing them!) or playing with veg peelings, helping tip things into pans etc. I also used to have high chairs in my kitchen so DC could watch what I was doing, try bits of food and bang wooden spoons etc while I cooked.
Assuming you have a partner, don't make cooking solely your responsibility unless that's what you want. It's easy to start taking on this stuff on mat leave then you never escape because you're more clued up on it all.
Agree with meal planning, I don't do a regular week but think of a few things we can have and only buy ingredients for that. Leaving it til the last minute to decide what to have is much more likely to result in having junk food!
Our regular meals include chicken or pork souvlaki, halloumi kebabs, chicken korma, pasta with bolognaise or pesto or tomato sauce, stir fry, sausage and mash.