I had a friend who's ex turned his kids against him. But now that they are adults, do NOT attempt to contact your ex to try to contact them. Since this was her plan, there is no way she would tell you anyway. Google, Facebook, or My Space their names or hire a PI to locate them, if you can. But when you do find them, I would recommend you write to them first...don't call or make physical contact with them yet. When you write to them, do not defend yourself.....because you have nothing to defend. Remind them of the good times you all had together. Actions speak louder than words and since they are adults, hopefully they will remember what it was really like when they were with you........not the lies that their mother verbally fed to them. Tell them that you always have loved them and always will.
You may not get an answer right away. I would wait a minimum of 6 months before writing again if you don't hear from them, but do NOT try to contact them in any other way until they respond to you. It appears they have a lot of mental abuse/PAS they have to work through, so take it slow with them. If you write them again, do the same as the first letter, write of shared memories and how much you love them.
But you must also realize there is a possibilty that they may never come around. You can't force them and if the PAS is too ingrained, they may not be able to see the truth through the garbage they were fed. I am telling you this, as this is exactly what happened to another friend of mine. He lost a lot of his vision in the VietNam war and his ex poisoned their daughter so badly, she wouldn't even tell him when she was getting married, let alone have him give her away....the daughter claimed she 'didn't want a blind man giving her away'. So sad. I have tried to explain PAS and how incidious it is to him, but he doesn't understand it. And now he also blames his daughter, who now has a son of her own. He's angry with her because he feels that, since she is now an adult, she should 'know better'. That's not how brainwashing works...a person who has been brainwashed/PAS'd just doesn't one day 'see the light'. They're fed this garbage every day of their lives when their minds are young and impressionable, to the point that they believe it to be the truth, no matter what. And the only way to combat it is to consistantly feed them the real truth, so that they can eventually make up their own minds what is real and what are the lies.
I wish you the best on your search and pray that you do find them. But if you don't or have difficulty dealing with your own emotions regarding this, I strongly recommend counseling to work through the issues. Good luck!