I wouldnt allow my kids near those people, even if it is their father and uncle. Its better to be safe then sorry. if any of my girls were abused it would haunt me for the rest of my life not to mention affect my daughters future and relationships with men.
I would however allow them to meet with their father as long as i or someone i trust were present.
I know my viewpoint is a bit different but i have no tollerance for sexual abusers and rapist. Father or not father, he is still capable of causing damage.