If you'd tried everything to sort out the issues in the relationship, ie counselling for you both individually and also as a couple, and there was nothing to do to help the relationship, then it is better for all involved to part.

I've seen the damage a bad relationship has done to children, they don't need to see that as a "normal functioning" relationship, both parents need to be happy.

As a friend once said to me, there are 3 people in a relationship, you, me and us. All 3 need to be happy, healthy and functioning for everything to work.

I've been in an non-functioning, abusive relationship (luckily no children) and the best thing was when that relationship ceased to be, I am a lot happier in myself, as a person now than I was during that time. Also the lessons I learnt from that relationship have helped me the relationships I had after that, I knew and had the strength to get out of relationships when they ceased to work (yes one of those relationships there were children and they didn't need to see the issues, they'd had enough when their parents broke up, that had emotionally/psychologically/physically damaged them enough).

Good luck with it all and I hope you make the right decision for everybody involved.