I'm sorry you are in such a difficult position. Are you absolutely sure that your wife would "get" the kids? Have you spoken to a lawyer who specializes in family law?

Please make sure you do things to take care of yourself. Your kids are learning so much about life, love, and how to deal from you, and even in the most difficult of times, they are watching. If you take care of yourself, you'll be able to give more to them.