Your perception check was pretty sweet, so definitely the Korrud order to halt his wolves. Probably not the exact whisperings of the main group though, although you'd hear some soft muffled voices coming from them. It looks like you'll see a slave trying to maneuver to the back of their group too, and notice that shes making a somatic movement. Sound fair?
I think its alright for Gimlak to know which direction to run, as his darkvisioned companions would be sharing info. He'd have to run a bit before actually seeing the Korrud for himself though. If you want to do this, we can trigger round one and initiative rolls once he is 15' away from them. At least this way on round one you can get an attack in too. You won't exactly have surprise as they are already suspicious, but the last thing they expect would be a slave to run on in
Does this feel right to you?