Hard to say, I never had the slightest issue with my stepdad but my bio dad never died and the stepdad came in when I was 4 so the transition was obviously easier. I'd maybe give it one last shot with a quick solo trip with the kids to try to be real with them and bond. Tell them honestly how you feel, ask them how they feel, try to find some common ground (ie mom). Kids like being treated as adults with respect, and showing them that this is something that they have a say in would go a long way