Sounds like a good shot in the making!
I do think you'll need some ND filtration to get a slow enough shutter speed. Is this going to be colour or B&W? How about B&W Infrared? Suitable filtration will slow that down to suitable levels.
Alternatively, this sounds like a job for a pinhole camera Attached pic was 1min exposure I think (going off memory here! but my son only hung around for part of the time