OP, you’re having a bit of a hard time on here, I think.
I have a high pressured job and the times I have been most stressed in my career I have gained pounds rather than lost. I’ve never understood people who don’t eat when stressed. The same happened when I had a baby who, for months, didn’t sleep for hours on end every single night. The exhaustion made it harder for me to make healthier choices like taking even a little more time required to make nutritious meals and go to the gym. We can crave sugar and carbs when stressed. So I get that part. Yes, we need to be more disciplined, everyone will tell you, as if we don’t know that.
However, you need to deal with the reason for your stress, which is seemingly a contributing factor in your weight gain, and it sounds like it’s the imbalance in your marriage. My husband is also a City banker and has a senior position managing off-shore teams which can mean calls and meetings around the clock. But he’s also a hands-on parent who has always helped during night feeds and wakeups.
It will be hard for you to turn back the clock as it sounds like he has become accustomed to being treated like a child by his wife. You need a conversation where you make it clear this will not go on a moment longer and why this is important: for you, your children and your marriage too. Your children need their mum for as long as possible; they need to see healthy role models in terms of your eating habits. McDonald’s should be a rare treat for adults and children. They also need to see a happier/healthier relationship where men don’t just earn the money and not lift a finger with everything else that contributes to looking after and raising a family.
In terms of quick fixes, I’d be choosing a couple of healthier cereals each week. Have a constantly full fruit bowl (another on your husband’s desk) for the days when your husband claims he is even too busy to spend the seconds it takes to pour some into a bowl with some milk. A piece of fruit will also make cereal more balanced for children and you too.
Lunch would be a sandwich and, for your children, healthy snacks including a different piece of fruit and some kind of salad/veg sticks with a dip like hummus, Greek yoghurt, pieces of cheese etc... If your children will only eat sugary yoghurts, try mixing some fruit into it like blueberries. It sounds like you don’t really need to worry about making packed lunches for work for your husband as you can afford for him to buy lunch on office days. They are plenty of Prets etc and it’ll take a minute for him to pop in for a sandwich, soup or salad.
By keeping breakfast and lunch simple to start with, you just have to meal plan dinner. If I were you, I’d make some choices you can have over a couple of days to save even more cooking time to free you up to rest and have time for yourself, perhaps even to exercise: lasagne, curries, saucy pasta dishes, salads, soup with crusty bread… Fair enough if you do all the cooking and that’s your choice but I would encourage him to start learning simple dishes on the weekend at first. Otherwise it’s going to fall to shit when you decide to make plans one evening.