I want my son to be able to trust me. I want my son to respect me. One of the ways I can ensure these is to always be honest with him. I want to be able to assure him that I've never lied. I want him to never doubt me, because I've never given him reason. And I want to lead by example.
This doesn't mean I believe he'll never lie to me. I'm certain he will. But I'll continue to model, continue to do what I know is right, continue to set the example that was never set for me. If I tell one lie, just one tiny lie EVER, that will all go out the window. I will have lost all of it. He will never be able to implicitly trust me, he will always be able to justify lying, because I lied to him.
So, I won't do it. I refuse. I refuse to lie to my son.