I've flown over 10 years and find most Captains are willing to have children visit the cockpit - some however do make them feel far more welcome than others. I know of one AN Captain who had a bad experience he's never gotten over, a child projectile vomitted all over the 767 centre control panel. Perhaps one can understand him not allowing visits. A far more imaginative excuse than simply too tired. Perhaps "Captain Too Tired" should get off fatigued and let someone else make his money!