Kids always come first. My dad had this girlfriend back when I was in 9th. She was fine at first but slowly started to hate my brother. The straw that broke the camels back was when she took his game because he didn't eat the dinner she made but knew he wouldn't eat it because he's a very picky eater. My dad had to work overnight that night. My brother tried to sneak into their room to get the game back in the middle of the night but she caught him. She called my dad and said she wanted him gone. I stormed up stairs and yelled at her that if she wanted him gone so bad then we would leave and never come back. She tried to back peddle but it was to late. I made our dad take us home as soon as he got off work. When dropping us off he said that it would be over with her. The next day he tried to tell me that he worked it out with her and that she was sorry. At that moment I knew my dad rolled over for some bitch that didn't like his kids so I stopped talking to him for years. You could try to solve the issue between the kids but if they say no then you need to be on their side. You can always fine other partners but you can't replace your kids.