A bit unreasonable, yes. Imagine you were still together and she got cancer and couldn’t look after the kids – your employers would be bound to give you time to deal with your personal life under the circumstances. You make it sound like it’s your ambition rather than your employers’ intransigence. I don’t know if that’s true. Ok, it’s a shame you’re not together, but she is still the mother to your kids, and you are still a father who is needed by your children. If you have the money you can look into childcare of some sort, but you’ll have to be reasonable and negotiate with your ex and explain that the only alternative is to do this or risk your job. She might well understand as her circumstances have changed and her own parents aren’t able to help all the time (nor should they be expected to). You all have to do your bit, whatever the cost. I say again, she is the mother of your children. You don’t have to love her, but if you love your children, their mother will always be in your life. Cherish your ex for the gifts she has given you. When she’s well, things will return to normal and you can focus 100% on your work again. If your employers won’t give you time then you can probably pursue this.
Don’t get me wrong, my ex and I loathe each other right now, but if she had cancer, not only would I be there for the kids whenever, I would be there supporting her, going to hospital visits, whatever she needed. When she is well, she can hate me again. I just couldn’t treat a Human Being any other way, let alone the mother of my children. If she is ill or dying or whatever, how awful would that be for the children? And if they’re hurting, I’m hurting.
It’s a no-brainer. But, it’s your life, your decisions.