Lying - Am I Really A Ninja?

There has been much talk of late into the morality of lying.  Can one lie "for a good cause"?
Two posts seem to cover the topic well - one by Father Jacob Maurer and another by Kevin O'Brien.
Basically the Church teaches that lying is evil by its very nature - that is, intrinsically evil - as per teh Catechism of the Catholic Church:

Lying is the most direct offense against the truth. To lie is to speak or act against the truth in order to lead someone into error. By injuring man's relation to truth and to his neighbor, a lie offends against the fundamental relation of man and of his word to the Lord. - CCC 2483

We follow this principle and agree.

Why am I raising this now?

A cleverly camouflaged Ninja.

For some time we have a running story at home that I am really a Ninja.  All the time I am away I am on secret Ninja business.  My apparent inbuilt lack of speed and dexterity are just a very clever ruse (so clever no one has uncovered my secret).  Superman could conceal his identity by wearing glasses, but I go to much greater lengths with a body shape carefully shaped over time with love and good cooking.
The older children don't believe this but Clare and Rose aren't quite sure.
The other day Clare asked Lana, "Is Dad really a Ninja?"
Lana (hiding a smile) replied, "Well, it's hard to tell.  He hides it very well at home, but he is away a lot.  Even I am not sure."
With a slight frown, Clare went away still unsure.

So, the question is, do I reveal to Clare that I may not really be a Ninja?  Am I leading her into error by injuring her relation to truth?