After a quick AVP benchmark run, I disabled crossfire and had no issues running scrypt on both gpus, without having to reboot. Then I stopped mining with GPU0 and ran AVP while GPU1 continued to mine.
That last part isn't new to me as I have flipped between the gamer/htpc/miner mode many times before. You'll be ok as long as GPU0/ the main display, is run at stock speeds.
I'm using the 13.9 drivers with the 13.5 CAP1 app profiles, btw.
gl xD