Code review is an excellent practice, particularly if it is done by developers to share knowledge, and the ground rules are set ahead of time that suggestions and criticisms are meant to be CONSTRUCTIVE, and not to use an individual developer for target practice.
Managers who are not developers will be greeted with suspicion by developers if they decide to do code reviews. Most manager types will not want to get into the detail that developers inherently get into when looking at code. Most managers will also not understand why the developers critique one approach over another.
If you are wanting to showcase the good work developers are doing to management, then "code review" has a different meaning, and should not be as detailed as code reviews that are done to instruct/improve code quality among the developers. This kind of presentation could be helpful in demonstrating what developers do if the presentation can be higher level, and less code-specific, focusing on what the managers understand (value, ROI, etc). It might make managers understand that Joe has added significant value to the company by building X, which we can show saves Y amount of time, or Z dollars per order, etc. I think it might be worth the effort in showing the value of individual members of your team. Remember, however, that you need to be careful you don't overwhelm your audience with jargon, or too many levels of detail.