Violet, where is the evidence that children are fine in estrangement situation? Parents might think so, as when children are tiny everything mom says is true to them, no question, as they develop for a quiet life they don’t rock the boat, as they get older they question, if indeed they have a mind of of their own. They will probably find out about cousins, of grandparents etc, visit and decide for themselves, especially if mom is lacking in certain areas or difficult.
Children benefit from grandparents, aunts and uncles, of course if there has been mental or physical abuse that’s different and I believe when ready the children need to know why. So many times it’s used as emotional blackmail or jealousy.
I know you had an abusive and cruel mother and obviously you wanted to protect your children from that, but that’s not always the case.