Does the father have to pay for the children to travel to visit their divorced mother?

No File Exists
Check below answers in case you are looking for other related questions:
The difference between khula‘ and talaaq
He divorced her for the third time and is saying that the first divorce was during a period of purity in which he had intercourse with her

No File Exists
Related Answers:
Is artificial insemination regarded as taking back a wife who is revocably divorced?
If he said to his wife: “Go back to your father’s house,” does that count as a divorce (talaaq)?
He made her divorce conditional upon her disobeying him, and she disobeyed him concerning something that came before his making it conditional; does the divorce count as such?
The difference between khula‘ and talaaq
He divorced her for the third time and is saying that the first divorce was during a period of purity in which he had intercourse with her

Recommended answers for you:
Ruling on dyeing the hair red and yellow
Hitting one’s wife?
Names whose use is forbidden
There is nothing in Islam to say that anal intercourse is permissible
Ruling on eating horse meat