Infidelity Support Group
Any relationship in which one partner engages willfully in sexual relations with another outside of the partnership is considered to have experienced infidelity. This breach of trust is often traumatizing for the faithful partner as well as the relationship, and support is often needed to heal emotionally and to decide whether or not the relationship should continue after...
If he wants to return to you and the family, it MUST be on your terms not his. If he expresses that desire, you have a decision to make. Make sure that he earns his way back--the OW has to go---like yesterday! No contact with her and complete transparency with you, including giving you access to his phone, e-mail etc. But I would not even go down that road unless you believe him to be really sincere.
If he has decided to go to therapy and change his character and you see a whole new person in his whole life, then you could make a decision if he is someone you would date and take it from there. Otherwise, I would cut the cord and have no contact with him, except for children things, if you have them.
An affair is in effect, a non-legal divorce. Some people get the divorce first, and then see if rebuilding takes place or not. Divorce isn't the final word, but put the load on his shoulder to make things right.
Sign the divorce, take what is yours.
Don't look back
Still, I am inclined to agree with Cole. Divorce is not the final word.