Greystone Mansion?

Greystone Mansion was used for the theatrical ending, specifically the wedding scene where the kids confront Corrine, she and Cathy get into a fight and Corrine falls off the trellis. The reason why Greystone was used is that it was decided to change the film's original ending because it didn't test well, but by the time they had a new ending written, they couldn't afford to go back to the Crane estate in Massachusetts, which had served as the exterior of Foxworth Hall in the movie (some of the interiors were used as well). In fact, several different locations were used for the mansion's interiors; the Pasadena Historical Society aka the Fenyes Mansion in Pasadena (which had dark red paneling) was used for the grandfather's bedroom, the dining room, Corrine's bedroom, and a few of the corridors. The ballroom scene was filmed at the Doheny Mansion at Mout St. Mary's College in Los Angeles, while the attic, bathroom, and bedroom where the kids were imprisoned were on a Hollywood soundstage.

This video shows the parts of Greystone that were used in the film:

https://www.youtube.com/watch?v=NsP_CP_RxGY