Where to book a house for a Wedding After Party on the Northshore

I would look at AirBNB or VRBO in the old Mandeville area near the lake since there are bars and restaurants in the area
Probably going to be hard though to find someone to just do a weekend rental of a big house.

Look into the rental cabins in Fountainbleau state park. They are on the water and a couple of them are pretty big. Plus they are remote so you won't get a ton of complaints partying it up.

If you try to "party" at a B&B in Old Mandeville you will have the police called on you in about five minutes. If you stay in town, be prepared to do all your partying at one of the bars.