What if I ask my girlfriend to look after my kids?
What exactly does your girlfriend need to watch your children for?
I would rather party
I understand wanting a break from parent life, but if you'd rather party all the time than spend time with your children, that's an issue. You cannot expect anyone else to raise your children while you party it up.
My friends won't think I'm a bad parent, they like to party too.
It doesn't matter what your friends think. What matters is being a responsible parent.