Along w the advice above:

As difficult as it may seem, smile and be pleasant and confident around your kids and your wife....it will drive her nuts!!! 

And if she is being negative about you to the kids and you smile and are pleasant and confident and do not say negative things about your wife they will eventually see the light and make up their own minds.

'If you can't say anything nice don't say anything at all' is probably an especially good rule in this situation you describe.

Best of luck.

Jim at Dawn

Try to also get out of the house and be with other people as much as possible. jmho.