The way I see it, that is a perfect opportunity for you to explain and guide him/her. This is what I meant that such movies will expose children to history and invoke interest in these topics.
But there is no denying that those times were different and the values were different. And we can explain these to the children. For example, we can illustrate how in Time1, they had Values1 and as time changes it became Time2 and values changed according to time and became Values2. Some subset of Values2 are disconnected or connected with Values1.
If the kids don't open and ask us questions; it is one of the jobs of parents to discuss movies with the kids.
Modern movies are tools like our puranas - to explain the values that we want to inculcate in our children. Conversations with children can be very taxing and engaging. They constantly challenge and stretch our thinking. It is a huge learning exercise.