1. Do nothing - grin and bear it.

2. File for legal separation. I know very little about this approach, but hopefully someone with more experience/knowledge will chime in.

3. File for divorce and leave this woman.

For option #3 ...

Now, keep in mind that unless your wife is shown to be a danger to your kids, she will most likely be awarded custodial parent (CP). What this usually means is that you'll end up paying child support (CS) to her and become and every-other-weekend (EOW) father - IOW, see them 1-2 nights a week and every other weekend (IF SHE ALLOWS IT! **). Most likely the affair will have almost no bearing with regards to the divorce, child support, and child custody. I'm not saying this to scare you into staying with her - only what to expect as a father who wants his children but cannot stand his wife.

If your wife is civil and understands the children's need for their father in their lives on equitable terms, she will either award you the CP or be open to a favorable (for you) custody/support agreement. If not, the law is NOT on your side as a father.

(**) - CP's routinely make an "excuse" to miss having the NCP pick up the kids. This is illegal, of course, but is done a lot because the CP's realize the courts very rarely enforce the issue.