I can't figure out how to make a npc say the dragon shout while they are using it can anyone help?
In Magic > Magic Effect you will find all of the current Shouts (they all start with VOICE). You can assign which sound plays, for which shout, to the right hand side (as well as other effects).
You can make new, or edit existing sounds ... including Shouts ... in Audio > Sound Descriptor ... the Shouts start with VOC. Here you can add or change individual sound files for each of the "words"
Also is it possible to get npcs to use dragonrend?
It appears to be possible, but it is not straight forward.
http://www.creationkit.com/Class
So you can add Voice Points to a new class that you create. You can then assign any Actor to that Class. BUT, you will have to script (somehow) actually giving and enabling Shouts for that Actor