Alternative expression for 二位小姐
I know we might be slaying the slain but seeing as you're asking for an


  [a]lternative expression for 二位小姐


it might as well be said.

MDBG defines 小姐 as:


  young lady / miss / (slang) prostitute / CL: 個｜个, 位


with prostitute being the operative definition. 

Seeing as 小姐 is so stigmatized - I believe most people tend to stay far away from it. 



二位 on the other hand is usually better put as 两位.

两位 is a very common expression for two people you don't know and you don't even need to classify it with guys/gals/whatever.


  两位，慢走