on the meal planning front, a system that helps with decision fatigue is having a theme for each night. So Monday might be veggie, Tues pasta based, Weds rice or noodles, Thurs leftovers, Friday fakeaway, Saturday X with chips, Sunday roast. Your meals change from week to week, but the themes stay the same.
Making sure that there's always something quick and easy in (e.g. frozen pizza, pasta and jars of sauce) helps for those nights when you really can't be bothered but need a meal on the table fast.
One of the best steps forward we've taken towards stopping the mental load falling entirely to me is a shared calendar so we can see each other's schedules. It means Hubby can't claim that I never told him about event X. We have a 'control centre' inside our mug cupboard (sounds odd but its because I hate visual clutter. Locating it in one of the most used cupboards in the house means we still see it multiple times a day). We have a paper calendar containing all birthdays, term dates bin days, appointments, and reminders of key things happening that month (e.g. sort MOT by date X). Next to this is a small magnetic whiteboard where we write our meal plan for the week and list anything that we need to pick up when we do the next shop. Inside the tea & coffee cupboard there is a pin board (made by sticking cork placemats up with double sided tape). Here I stick to do lists for the week - if hubby can see it, he's far more likely to take on a task without me having to ask/delegate/nag/remind.
think about tasks you can batch to save future you some time - e.g. why go to the shop to buy 1 birthday card when you can go armed with a list and buy all of the cards that you will need for the next 6 - 12 months? If you can afford to, buy loo roll / cleaning supplies / toiletries in bulk so it's one less thing to worry about.