For Windows computers that are powered on and are online, Google Update will update installations where Chrome is not running. No user action is needed.
Could you explain a bit more what signals the monitoring is reporting? How is it determining Chrome's version, and what is it comparing this to to determine that Chrome is out of date?
Note that if Chrome is running when an update is applied, a browser restart is required. Users failing to restart in a timely fashion is a common source of administrator frustration. This is the scenario that the policies I mentioned previously address.