Freaking out about it for months? Surely that's an exaggeration. A powerful film, yes, but does any movie really have that kind of power anymore?
A child would probably be bored to tears by this. Still, you never know. I remember one writer on horror movies, Kendall R. Phillips, talking about his young daughter watching the 1931 Dracula without batting an eye, but when she came in the room during the scene in the 1931 Frankenstein, when Karloff first appears backing into the camera and slowly turning, she ran away in fear.
A fair few movies still have the power to freak me out - and I'm 33! The power of a film very much depends on who is watching it and the disposition of that person. That's my two pence worth! I'd let a child 10+ watch it, if they wanted to, and talk them through it. Very well done film!
I would say that for most modern children, this would not be of much interest, though of course there are exceptions. To me, it requires a certain maturity to properly appreciate. When I first viewed it, I think I was mainly struck by its strangeness and probably didn't quite comprehend it all. I've now seen it 4 times and really love it. For such an old film, it still manages to be eerie, provocative and unique.
and talk them through it
One of the joys for me was understanding the story and what the characters said to each other simply by watching them act. There are intertitles, yes, but not for all dialog. The acting is good enough though that you can piece together what the characters are saying to each other even in those shots that don't have intertitles. If you talk someone through it, you take a piece of the joy away in my opinion. If i would watch this with a child i would sit next to them, watch their reactions and explain only if they had questions.