sweet lady, I'm sorry to hear that your ex plans on seeing his children once a year if that. He has retained his joint legal custody to protect himself if his situation changes with the g/f. I would, after one year of documenting everything, go back to court for legal sole custody due to the fact he has only visited X number of times in one year.
Its too bad that at this point in his life, his g/f is more important than his children. Unfortunately for him, as mrd says, he will regret that with all his might, when its too late.
Once the kids are older, guess what, they won't want to visit with their Dad. Nothing will make up for years lost with them.
My son was very young when we separated. I bascially forced him to keep visiting with his Dad even though he hated going there because of his lunatic g/f then wife. I knew there would be a point when he would be old enough to say "i'm not going", and that's exactly what happened. No one can say that I prevented him from going and he was able to make up his own mind when he was twelve or thirteen.
Sometimes its better if you have less contact with the ex, however its not so good for the one raising them and having to explain why their father doesn't visit. He will live with his decision every day, and I'm sure he'll be regretting it. If she was any sort of decent person, she would encourage him to make sure he visits as often as possible.