To make it quicker, I make a selfquote:
"That is rather easy, depending what path you are on! For the romance and happy sharing/swinging paths it is easy to get, for most hard NTR stuff difficult to impossible.
You need(!) to win the jogging run during the weekend hike, have 7+ points in charisma/intelligence both and 6+ love points with your wife at that moment (higher Stats are better here). During the stretching after the run you can convince her to some naughty fun. She will give you a blowjob in open public, which also unlocks her budding exhibitionism."
As for your second part of the post, I am sorry, but I do not understand which trait route ntr you mean, this is not specific enough.