Wow, I don't know what to think about this.. He violated a custody order. Bad. He raised his kids all by himself. Good, considering what most dads do, however thats mitigated alot by 90/10 female/male custody battles.
At this point.. Breaking up the family causes more suffering to the innocents, than to the guilty party.. But he obviously must be punished.. But what punishment would be sufficient? Hmm. Very difficult..
Well, I think what should be the final consideration in this, is find out WHY the daughter wants nothing to do with the mom. Find out what she was told about the mom growing up.
Then take whether or not the CHILDREN want to press charges on the father for what happened. Because lets face it, custody is something thats "for" the kids, not because she DESERVES to have them more than another. Custody isn't a possession, it's a PRIVILEGE. If at their age (basically adults) if they don't want to, no crime should be prosecuteable.
So take those two together, and come up with something reasonable. Obviously, as a single father, jail would destroy the family, so there are other ways. Just have to get creative.
This is a unique case, it needs a unique answer. Not just a generic: Go to Jail!!!