Just a point of clarification. The past year we have been living apart I have been encouraging H to spend more time with kids, inviting him for dinners and encouraging the kids to be patient with their dad etc. this was all while he was simply saying that he was unhappy and had to find his happiness. He went on a vacation by himself for "Family Day Weekend" ( that's a newish holiday we have up here in Feb) and I helped pay for that. We were all being so accommodating to him a the whole time he was lieing and a having an affair. He has been keeping it secret because it is a workplace affair and he is her immediate supervisor. Anyway it was just a couple of weeks ago that the kids went to talk to him and actually "caught them in the act" literally.
So it is not that I am bad mouthing their father - I never have - if anything it has been the opposite. But kids now realize the lies and complete disrespect their father has shown all of us.
H wants to just pretend nothing has happened. No apologies, no explanations.