This is really the only issue here. If she is willing to cheat on her husband that is her fault not yours if you aren't pursuing. HOWEVER, if you have ANY shred of integrity, morals, decency, or a soul you will won't fuck up those kids lives. My parents are divorced, and it really is hell, even though I don't show it externally. If you fuck up a married couple with children involved, I do not respect a single thing about you.