Personally I would have presumed you could not reuse crown caps.
Would they not be deformed after use with a bottle opener? I would hazard a guess that if you reused them, you would not get a adequate seal on the bottles to allow carbonation.
I personally have tried this but maybe someone else here might have.
Well you have a good source of bottles. You can pick new crown caps up relatively cheaply online and at the local LHBS. I love to reuse and recycle but sometimes we do have to bite the bullet . You would not want to lose 5 gallons of a new beer.
You can get away using Grolsh type bottles if you have these in the bar.
it depends...
if the bottle opener has deformed the cap, and the whole thing has a line across it, then probably not.
However, if the bottle opener has only pushed up the edges of the seration, and the top is still flat then possibly, yes.
I've re-sealed a crown cap bottle before now, and had to use mole-grips to do it, but it sealed perfectly ok.