Hi joshuajp4191 -- this functionality isn't currently supported in cnMaestro: the SM devices will require connectivity in order to update the software. There is a section in the User Guide (PMP Configuration Prerequisites) that details how the system should be configured. Leveraging the AP to more efficiently update the SMs is something we are considering for cnMaestro, but it hasn't been committed yet.
The only way to do what you want, with your current configuration, is to use CNUT. Not only will you be able to perform the update, but you will also be able to schedule the update to automatically start at a time of your choosing. Something else you can't do with cnMaestro.