Really admire you mate, I think most guys would be only to happy to leave the kids with their ex and go back to the single life.
When I got together with my wife, she had 2 children (girls) both with different dads. In the 10 years we have been together, their Dads have taken next but nothing to do with them, and have let them down more times than I care to remember. There has been zero financial support either.
I aint with my kids father but they have the most amazing step dad who supports them more emotionally and financialy too.. They dote on their step dad.
I admire men who are willing to be single dads my cousin is a single dad and i admire him for what he has done and he works to on his dads farm has lots of help from the family. I think dads can be just as good single parents as mums.