I'm the guy that which does Love and Capes.
You don’t mess around with Jim. Or Abby.
In a world of superheroes with secret identities, Mark can hardly be the first one with this problem.
Speaking of which, how do you keep a secret identity with a little kid around? I’m thinking that the age of five to twelve or so would be the most difficult. Big enough to understand that daddy is a big hero, but not big enough to be trusted with a secret. What if he/she is picked on? How to prevent the temptation to say: “Well, *my* dad is the Crusader and he’ll kick your butt!”
Yngvar: “Ohh, suuuuurrre your daddy is the Crusader! And my mommy is the Empress of the Galaxy!”
However, you’re right: The urge to bring Daddy to “Show-and-Tell”, as it were, would inevitably become overwhelming.
About knowing the real identity, try to read animal man of Dc comics: A entiry family dealing of the super powers of the chief of family, animal man. You can read how the main character become a cool father.
Or the occasional rescuing of the school bus and saying: “Thank you, daddy.”
© 2015 Thomas F. Zahler