Legal Question in Criminal Law in California

I've never heard of anything like that; sounds like an Urban Legend. How would "they" connect the children to the father in the first place? Maybe some other attorney knows something about it I don't. If no one else posts, I would not worry about it. ;)

The authorities to not abduct innocent children in order to extort parents into surrendering. Unless there is some independent ground for them to take the children, I see no reason to worry.

Merely having a parent with pending charges is not enough reason for the authorities to take the children unless, perhaps, the charges show that the children are in real danger (as, for instance, if the charges relate to child abuse). Even then, I don't think the California authorities have jurisdiction over out-of-state visitors unless some new incidents occur while they're here.