From what I understand, the Mt Vernon/Mahopac incident was overblown. My children knew Mahopac students. They and their families were very friendly and not in the least bit racist. I really wouldn't worry about it.
I will say, my sons attended Archbishop Stepinac High School in White Plains. One of the benefits, besides a great education, was the diversity of the students. Not only diverse in race, but in economic background and, oddly enough, in religion too. Something sorely lacking in the Yorktown Central School District (I wouldn't send another child there for many reasons).
Recently, I heard that families move to White Plains because of the low taxes and save for private schools - although White Plains Public High School, like Mahopac High School, is highly rated.
White Plains High School Ranked Among 100 Best in New York | White Plains, NY Patch
Best thing to do is tour the schools. We ruled out Pawling after a tour of the high school. Have lunch in town, go to story time at the library, it's only by being there that you can really judge it.
Mahopac probably has housing for rent, try it for a year.