You don't have any control over your wife and if she wants to go out, she's going to do it. Step back and cease trying to tell her what to do because it's only going to make things worse. You only have control over you and your son.
Let her go, but document everything because you may need that documentation down the road.
However, I would not back down about the inlaws...they should still stay in a hotel.
If you need to go out, get a babysitter and do not rely on her.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
