Steel Rod.
Can't you see you've argued against your own point in one paragraph.
You say you have no issue encouraging flight deck visits, yet by so doing you are publicising (to the visitor at the very least) that they are possible upon request.
Presumably you know that and read the 7 year old concerned extracts from the official secrets act, threatening imprisonment should be divulge the details of such visit at show and tell on Monday morning. Or do you follow him around in your SUV with the dark tinted windows?