Loafers, I read your OP and your other reply.
I wanted to respond as fast as possible so I haven't read any of the replies yet, sorry if I am repeating anything here (I am sure I am)
Firstly, I beg you, please please please do not under any circumstances, take your children to Iran. Do not take them out of this country to meet him. Under ANY circumstances. If he cared a jot, he would come to them.
Okay, I think I made myself clear on that one.
This story is very close to my heart. My story is similar, except I was the DD2. My father pretty much did this to us.
For the record, my mum used the excuse that he was "working" abroad, and I just accepted that. Really, I knew they were divorced, as I had found the papers when I was really little. I understood that they were not together and it did not bother me. My older sister, like your DD1 was effected more at the time, as she was closer to him. But we just accepted it and in the main, forgot about him. My mum would warn us occasionally, that if we ever saw him near our home, never to go anywhere with him. She was terrified of abduction.
Anyway fast forward 20 odd years, my mum, my sister and I are so very very close. Us sisters have never blamed our mother, ever. We have nothing but respect for her. We know that if our father really cared for us, he would have come back to us.
And the same is true in this case. What is stopping him from coming back here? Do not trust this man. He up and left without any warning - to another country! He abandoned his own children. Can you really trust him? Is he paying money towards their keep?
Sorry, I hope this message makes sense.