What can we do to keep the prior owners of our house from coming around to reminisce?

We recently moved into our dream home in New Jersey and have been living here for about 7 months now. The home was sold to us by an elderly woman whos husband ped away the year before and who also lived with her 30-something daughter and young granddaughter. The seller was very attached to the house, having lived there for 40 plus years, and said that she had to sell due to the high cost of living and maintaining the house all on her own. My wife and I felt sorry for her, but at the same time were eager to close and begin our lives in our first home. It appears that the prior owners have been returning to the neighborhood, sighted by my wife sitting in their car across the street from the house for as long as half an hour, not causing any harm, but just sitting their watching the house. We had reports from our neighbors of the daughter coming by to look through the windows of our home when we were out. This behavior disturbs us both and would like it to end. What can be done?