Wow, that's a tough one, peace. I know exactly how you feel about him getting to "fake being a decent guy".
However, my C was very clear on keeping the kids "out of the middle" if at all possible. This does not mean lying to them! It just means not volunteering information that may hurt them. If they ask or bring up a touchy subject, I would say be honest but sensitive of their position. In other words don't vilify their father, but you don't have to lie either.
So, I guess I'm saying the ball is in your kids court. Follow their lead, and try to be as sensitive and supportive to them and respectful of their feelings for their dad.
And, I think you might be surprised at how much your 14 year old knows......
((((((hugs))))))
TJ
Me45,H49 D24,S18 M26,T28 Bomb 3/19/08 Sep 6/23/08 EA/PA with Secretary 2007-8 3/2009 H moved in w/OW2 7/2009 Let him go w/Love. 8/2009 Legally Sep'd