Hi, I appreciate what you're trying to say but I feel I need to clarify things.
The kids have absolutely no chance of keeping my ex's place tidy. She throws dog treats on the floor deliberately and they get trodden on and crushed. She piles up tea bags on the coffee table, leaves food around the place for flies to lay eggs in. This is her, not them. It's not their job to be her housekeeper, and while she is setting no example they won't spend their time picking up after her. It's not their responsibility. Furthermore, the younger autistic kid, while highly intelligent, is not emotionally mature enough to be expected to assist with household tasks.
As I've said, I am in the office 50 hours a week, 46 weeks a year. That's over 2000 hours. She works 25 hours a week term time only. That's less than 1000 hours. Despite this, I still have them every second weekend (including Friday evenings), two evenings a week (they go back to her place to sleep as it's easier for getting to school), two weeks in the summer, and a week at Christmas. I also make a significant financial contribution that leaves me with less disposable income than her. I really do pull my weight in this co-parenting situation, and I also know that any suggestion that I take the kids more often will not go down well with her. She seriously doesn't see the mess and dirt as a problem at all so doesn't believe she needs any additional help.
I also did all the cleaning when we were together. This is definitely a 50-50 arrangement. I even regularly look after the kids so that she can see friends or go to see bands etc.
Career progression. She isn't interested in career progression. From the moment the kids were born she wanted to be a stay-at-home mum. The decision to work part time was hers because she soon realised she was "bored" at home.
I do not leave her to do the vast majority of the childcare to her. I am heavily involved.
My children know the rules are different in my place. They always take their shoes off at the door, hang their coats and bags up, put things in the bin, put their dirty dishes in the bowl etc. They help with the recycling. At her place there is no example being set and there is no point them tidying up their own things when she makes no effort to tidy up herself. The mess isn't the fault of the kids.
When we were together it was almost impossible to keep the place tidy. I got pushed into the door of the fridge freezer once because I moved some Amazon parcels off the hob in order to cook something.
As for things improving if I pull my weight, she was this messy when she lived alone, this messy before kids, and will be this messy after they've gone. The difference now is that I'm not around to pick up after her.