if I understand you right, you want to do a InPlace-Upgrade from 9.0 to 9.6 SP2. Which server version do you have? 2008/2012?
I recommend to Update from 9.0 to 9.6 as a Side-by-Side Ugrade. So you are able to do this in your work time.
The following Howto describes the this:
Thank you for replying. Yes, it would be an in-place upgrade and the server is running 2008 r2 standard 64-bit. Unfortunately, we do not have another server we can use to do a side-by-side upgrade. With the in-place upgrade, is it correct in saying that until the all the devices are also upgraded to the latest version, we will not be able to connect to them?