Things To Do

https://www.earthtrekkers.com/paris-bucket-list-best-experiences-paris/
This is by far the best website list of recommendations! I've toured almost everything on this list so can vouch for it! My favorite was the Palace of Versailles :) you can easily do a whole day trip there and get a 45min train from Paris straight there easily.
In my opinion this church, Sacred Heart Basilica of Montmartre (Sacre-Coeur), is an even better visit than Notre Dame, but be ready for a long beautiful walk UP to the hillside of Paris to get there!
Also Musée du Louvre takes a full day as well & there is a cafe inside (you can do a half day if you only see the art main halls).
If you are looking for places to see in the countryside north of Paris towards the wedding venue then check out Beauvais, Amiens, and Compiègn, France.