I like the idea of 3PO thinking he’s there to negotiate peacefully, only to suddenly realize the humans are blasting their way through everything.

How does this sound: “I am here to negotiate for one ‘Chewie’”

That way he still remains an unknown to him without the line getting too long.

EDIT: Here is my favorite take of that line - https://drive.google.com/file/d/18MfDVaDKEUPDMfB_r9k39TtjFNjAetNZ/view?usp=sharing
I’d love for his follow up line to be a callback to episode II: “Oh my! That was rather aggressive for negotiations!”