One thing I would ask for in an addition is a safe place for severe storms. In the congregation I worked in children had to walk down a long hallway, go down two flights of stairs, passing two glass doors along the way. It would be much better to have reinforced rooms near the classrooms, or quick access to a safe place. Also, have well marked emergency exits.
All the things Jan suggested are good too, but I would add:
~ telephone for emergencies (not a cell phone)
~ weather radio
~ some kind of rapid information system to tell teachers quickly about approaching dangers, like a storm.
I know I sound grim, but I live in Tornado Alley and have had to take cover with the children on more than one occasion.
Keep us posted!
Blessings,
Julie Burton