There's a lot of pitfalls here. You're planning to go to a place you've never been to have a duo with two girls you've never seen? Sure it could work out great but it's is a big gamble. You don't know if you're compatible with either girl or if they are with each other.
My advice is to see each of them separately and ask who they like to do duos with, but without mentioning specific names. If they both name each other then go for it. If you mention the other girl's name they might just say yes for the extra money but not really be into it.
FWIW I've see both Avah and Kaii and I had a good time with both of them, but they were expensive so I haven't repeated with either one. I'd imagine a duo with them would be pretty pricey.