I agree with Devils Advocate. My young daughter would love to see what I do at work but these idiotic rules won't allow her to. I am expected though to allow access to cabin crew I don't know and who could have any type of background, so far unknown. As you say, Disclosure won't bring up their foreign activities and there are a lot of foreign cabin crew joining who haven't been in this country 5 minutes. (And no, I'm not a racist just a realist)
As for JW411, I can't imagine anyone wanting to be up there with him anyway with an attitude like that!
So yes, I think immediate relatives of the Capt/FO should be allowed to travel on the jumpseat. I worked hard to get where I am with the support of my family. Why shouldn't they be able to get some pleasure back by being able to witness the fruits of their support?