Is there an non evil outcome for the Preservation of Beauty quest?
Solution 1:
The very same walkthrough link provides you with two options to drive the Decanters off directly.
attempt to sell Rhin to the Decanted with Erritis in your party. Erritis will protest vigorously and if you persist will drive the Decanted off
Though, this will reduce Rhin's and Erritis' opinion of you.
If you speak to Parsim Flint, you will learn that the Decanted's intentions are rather more sinister than it made out. After two guests have been handed over, you can question the Decanted about what awaits them. If you prefer not to send anyone else to such a grizzly fate, you can drive the Decanted off for 40XP. You can also take this path if you have spoken to Parsim Flint.
So, the clear first choice is to talk to Parsim Flint, which should allow you to drive off the Decanted without selling anybody. If this does not work, you must resort to option 1 and just accept the opinion hit with those two companions.