" have the kids call me because I want to ask them about x".
I suspect this is another version of the heady mix of idleness and control. The short and long answer is no.
Whether you say it out loud or simply ignore his request is down to you. If you suspect is is a reason to have a fight then personally I would ignore.
Is there any compelling reason that he cannot communicate directly with them? I mean do they have not any kind of electronic device or do they live a secluded and simple life? Are they unable to speak, read or write?
While it is important to facilitate a relationship with both parents, you are not the intermediary if he can communicate directly with them.
