Wife must never know....NEVER 
This could be a problem.
If you're smart enough to lead a double life, then you're smart enough to know why it's not a good idea.
Just let the wife know who you are and what you're about and you'll experience a freedom like none you have ever known. Who knows, she may even decide to become the object of your offseason FBB fantasies someday.
Besides, the last thing you want is for the guilt you feeling about sneaking around on the wife to affect your ability to get it up for a hot musclechick who wants to bang you into oblivion.