I wouldn't call an affair in a home a "less than ideal" situation...
I also do not consider a person who cheats on their spouse acting good twoards the children...
Phil McGraw once said on his show "Being a good parent, means first and foremost being a good spouse... if you can't get a long with your spouse, your children suffer for that..."
Despite a children's apparent contentment they DO feel it.
I grew up in an alcoholic's household... I was a fairly content child too, but I do also realise how much BETTER it would have been if my home was booze free... I SURVIVED it and am not what I woudl call "damaged", but I woudl have had a MUCH better childhood without the addiction ravaging my home...
I consider mb's situation to be no different.. even if the children are content, I think tehy would and WILL be a LOT happier with an affair-free home...
And that's the Husband's choice to bring that into the home or to end it and act like an adult...
I am not going to gloss over the damage done to a spouse and suggest it will nto affect children.. I don't find that beleiveable at all