I beleive everyone has the right to change their mind, to move on.
My wife and I made a pact way back when we were first serious, and it is an unspoken knowledge between us even now 6 years later, that if one of us ever becomes unhappy, or wants something else that they say so. We know this would be awful but honest, and the other is to give full blessing to the other. That does not mean there will be no tears or heartbreak either, it just means that sometimes the gig is up.
True love will let another go if it means that one will be happier.
The stay away while i 'sort it out' is a dead giveaway though. Not of another involved nessicarily. In my own case with marriage #1, i moved out to sort myself out, never went back and broke her heart, but there was no other woman involved.
Just be there for your son. As a well known song (Gilbert Osullivan) said "nothing worse than being in love with one who isnt"
all the best in helping your son
oz