Yeah, I wouldn't cut off the son or discourage the children's friendship either. Youngest has a couple friends where the visiting goes one way for various reasons; there's lots of reasons why that might be the case, especially in the Covid era.

(And who knows? If both families are still in the area in ten years, the friend might need an adult to talk to about the old article he found about his dad, and "John" might be exactly the right person.)