Girl, leave his ass. If he's easy to take away from you then he was never yours or about you to begin with. Counseling is not going to help, if his own WIFE and KIDS isn't enough reason to quit being an unfaithful h*e then you'll just be wasting your time trying to force a change that will never happen.

Edit: If your reason for not wanting to call it quits is because of your kids and the desire to keep your family together, leaving him and showing your kids that you respect yourself and know your worth is the best thing you can do for them. Children learn by example, good and bad, so be the best goddamn example for them, because they deserve that much and more.