I think that it will work out well. Was he mad/upset that you are not going to Paris that day? How did he react? Did you get your ticket money back?
I think that the letter is fine, especially if it is something that is a custom. And if it doesn't go over as expected you seem to have lots of things lined up to do to get away from him and out of the house. So it should be fine. What about leaving it on Thursday for him to find after you are gone? Would that be too late? Just wondering if it would be good for him to have a good day/s with you and then read the letter. Either way is probably fine.
So now that you are not going to Paris on Monday have you reschedualed your session with Jody or are you going to wait until after Monday to tell her how it goes?