I'm good with this plan. Don't worry Lil sis, if there's one thing I know how to do aside from getting hit by blunt objects is speak in confusing and sometimes contradictory ways. It's the perfect thing for negotiations with disreputable people.
Maybe while that's going on Faer can go tell Ordhan and Falina what we're up to? On the off chance that they plan to go find themselves a slaver and say "Tell you're bosses we're here with three other Grey Wardens, two of whom are elves and two Qunari! And We're all gonna shut you down!"
...I am a little iffy though, a Mage is a valuable thing to have, Hissra isn't quite as expendable as I am should things go badly.