Years ago I saw a movie that I would like to see again, but I can't remember the title.
In fact, I can only remember one scene. It's not much to go on, but maybe it rings a bell.
It's a movie from the sixties.
A bunch of villains have moved in to a detached house, pretending to be a family, but in fact they're preparing a crime (a heist or a kidnapping, I really can't remember).
The house lies in a isolated place, rural perhaps, and there's just one house next to it where a family lives who doesn't know anything about the real identity of their new neighbours.

Is that something to do with kids? If it does not, don't count me for your best answers.

The family next to the villains had kids. I remember a boy playing in the yard while the villains where observing their neighbours. I can't remember if the boy played a significant part in the movie though.