Unfortunately, the school wouldn't allow me to use Nl3 inflators... 
As for the parachute deploying cleanly to work, I'm using a strap to tie it neatly to the underside / side of the drone so when the servo releases the strap, the parachute will fall out and gravity will do its thing hopefully. (just have to make sure the strings dont tangle...)
and if you're familiar with Mars Parachutes LITE / Mini, my design concept is pretty much identical to theirs.