Cactus, Havok has a new product out called Project Anarchy. This would be perfect for that and includes a tone map filter that has motion blur. Best of all it is free fro ios, android, and tizen: http://www.projectanarchy.com/
Unity doesn't have post-processing (which includes motion blur) in the free version, though. So you'll have to sacrifice that. I don't think your scene (looks to be rather lowpoly) will give any performance issues.