LS: First, my condolences regarding your grandmother. I am sorry for your loss.
As you may remember, I have been where you are. My wife went out of town to see her OM a few weeks ago. When she returned, wife expected me to be grumpy, passive-aggressive, moody, etc. She didn't get any of that. Now, she did not get a hero's welcome. On the contrary, I made it a point to be out of the house when she returned. But when I saw her again, it was as if she just got home from a day at the office.
The point is, when your wife returns, you need to not give her what she expects. You can look her in the face . And when you do, you will see a confused, frightened person. Somebody who needs a strong husband who is not afraid to go after what he wants.
Here's an idea on how to handle it. Try to have your son around when you are with your wife just after she returns. Make sure he is in the room. And look at him while you are with your wife. See somebody who needs mom & dad together. Draw strength from his presence; draw strength from his needs. You will have clarity, I promise you that. You will not yell, or get angry. You will have a strong sense of purpose, and you will know just what to do.