Here's my thoughts on reading what you wrote -- know that I know nothing about this category of law -- sounds like it would be GREAT if he removed himself parentally. Just think of all the pain/arguments you'll be spared if he never needs to be consulted about anything to do with the kids forever. What a load off you that would be! You would never have to be in contact with him about holidays, travel plans, moving, school plays, etc.
YES it would stink for the kids but what really stinks is that they don't have a good dad. But they wouldn't have a good dad if he kept his parental rights. What they would have is a lot of broken promises, fear and stress.
However, does HIM deciding to do this mean he doesn't pay child support? That I don't know. Are you dependent upon it to pay bills/live out of poverty? I'm hoping not because, as sad as it is, sounds like you'll all be better off without him in your lives.