strategy help - Low Lantern mage fight

The setting is Baldur's Gate, in the quaint little floating whorehouse called the Low Lantern. I hit the third level of the ship and that wonderful entropy-magewhore duo manage to chunk several of my party members. Need help getting around this without anybody getting chunked.

When I'm fighting a hard battle, I usually stealth my thieves and send them in with backstabbing weapons or exploding oils. I can't use the latter because of all the commoners roaming around, and I have difficulties with the former because the fast-moving sword-packing whore manages to chunk the unlucky thief who struck first in one move. Yikes.

I tried equipping my main stealth thief with several pain-dealing weapons and taking just her down the staircase. Here's what happened:

poison arrow = whoresave
ice/fire arrow = small damage
ogre mage arrow = um...just tried this one to see what'd happen. nope.
venom dagger and triple backstab = I chunked before she croaked
short sword +2, triple backstab, running around like headless Melicamp = this one was funny. I landed my backstab, decloaked, and ran away around the staircase. One followed, the other tracked, stopped, and began firing spells. Is it possible to cast Horror/Dire Charm on commoners? Because the other whore shot a spell at me and the surrounding commoners went yellow and either ran for cover or ran to whack me down. Felt like a game of tag. I was chunked, eventually, but managed to stay alive long enough to make my other thief invisible, bring her down, and kill the mage before the whorefighter chunked my other thief.

My gameplan now goes like this:

--stealth thief, bring to third level, wake up fighterwhore with a nice triple backstab
--run away, let her follow, hide behind people/items
--stealth other thief, bring her down, backstab fighterwhore
--switch to acid/poison arrows to finish her off
--recloak
--triple backstabber wakes up whoremage, plays bait while double backstabber gets whoremage in view and empties acid arrows into her sorry carcass. hopefully whoremage will go melee.

Thoughts on this?