I think somewhere in the 4100ES you can program the voice message.

With the auditorium, they should have a cutoff relay that shuts down a lot of the A/V equipment when the system activates.

What they should actually do in regard to the voice evac is put in a 4100ES with voice capability at the middle school section, or upgrade the panel with the voice cards. The same should be done in the HS section. That way you reduce the amount of sub panels that you have to support for the system.