I highly doubt we can sneak the prisoners out, as they're likely injured and/or malnourished, depending on how and when they were captured. The only purpose of sneaking, IMO, would be to put us in a favorable position for a devastating first strike.
Elsa, as always, is better off at the rear of the party and with a height advantage. She's an arrow magnet.
A distinct possibility, though by the time they do return, we'll have dealt with those in the ravine. So at least they won't outnumber us too badly at any one time.
The key to dealing with numerous opponents is to fight them piecemeal.