This review is based on my experience as someone unable to read Danish. This (free) museum is 70% crime, 30% police history and covers the civil unrest in Copenhagen in 2006 but is mostly artifacts from criminal cases. The guy at the front desk was really friendly and lent me the English language guide but I couldn't figure out which room corresponded to which page in the guide and the exhibits are exclusively in Danish.
If you can't read Danish, I'd only recommend it if you are a big mystery reader or are interested in the Denmark-specific police history as there is some stuff about the transition from nightwatchmen and the role of lighting in the city. But if you are in the neighborhood, maybe you'd want to check it out; it's free.
There are some bloody photos but I don't think they would be too disturbing for kids. read more