]I believe that if Darcy had brought more people than the Bingleys, JA would have at least mentioned that there were other ladies/gentlemen there. Darcy brought only four people with him, but perhaps to Mrs. Reynolds that would mean a "large" party.

I believe the four people you mean are Mr and Miss Bingley, Mr and Mrs Hurst. All four of them are known to Elizabeth, but Mr Darcy says '...among them are some who will claim an acquaintance with you, - Mr Bingley and his sisters.' [volume III, chapter I] I take it to mean there would be other people than the Bingleys.