You dont abandon your children because it sucks and it's overwhelming. That's what us mothers do, we stick around and raise our babies. The men run away and we keep the responsibility we committed to when we chose to birth them. I'm being harsh because it is deeply, irreversibly traumatic for children to lose a main carer but especially their mother. That ship sailed when you chose to have those children - you do not have the right to shred abother human being's psyche so deeply for your own benefit. Grow up. A father may be able to cut and run, leaving toddlers without a dad, that's part and parcel of being a man. Us mothers don't do that. Put your big girl panties on and raise the kids you chose to keep.
You have options, you can split custody or you can be a working mother. It's not easy but we do it and we cope and it's worth it for the children we created.