Late reply here, but hopefully this helps someone that finds this post.
First and foremost, there is an excellent set of checklists on 911.gov that will help you prepare from an organizational perspective.
Link here - https://www.911.gov/project_mltsdispatchablelocation.html
Second, you'll be best served if you deploy CER. It integrates natively with CUCM, supports wireless tracking if you're using Cisco WLC's, and provides a tight integration with notifications, etc. You don't have to use it, but you'll need something to do notifications for you (Native Emergency Calling is a bit too small for your size organization) and phone tracking.
Last, you will likely need a 911 provider unless you are going to manually update location info with your carrier (complex, not well understood even by your typical telco, and cumbersome to keep up to date). There are three providers for Cisco these days: 9Line (Link here), Intrado, and Redsky. I work for the first one.
Best of luck to you. Keep in mind Ray Baum's is now in play so you need to keep this on your radar.
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-Mark Turpin