From last Sunday's Gospel in the Ordinary Form (unless your priest went with the bowlderized reading:

"It was also said, 
Whoever divorces his wife must give her a bill of divorce.
But I say to you,
whoever divorces his wife -  unless the marriage is unlawful - 
causes her to commit adultery,
and whoever marries a divorced woman commits adultery."

I'm going to stick with Jesus' definition of adultery rather than yours. 

Does adultery become acceptable because a child is produced out of the union?  I have someone in my extended family, an older man who got a younger woman pregnant and left his long time wife, don't see him at family gatherings to be a grandfather to his grandchildren. Unless his marriage has grounds for nullity, does the fact the union produced a child change the fact the mother of the child is with someone else's husband?