Groundhog Day.
In 2006, the film was added to the United States National Film Registry as being deemed "culturally, historically, or aesthetically significant". I think the Americans have got it absolutely right: this is not only one of the best films ever made but it is also a wonderful, light-hearted study of life.
I'd invite my grandchildren over to watch it with me and I'm sure we'd have a few 'eek' moments at the drama; a few 'aaw' moments at the love and quite a few 'laugh out loud' moments at the comedy.
The children are just beginning to understand themes or messages in books so, afterwards, I'd ask each of them to tell me what messages they thought were being delivered in the film.
I might also throw in that perplexing mathematical question: 'How many days did Phil spend in the time loop?' to see how their maths is coming along!