In Chapter 2 of Pride and Prejudice when Mr. Bennet surprises all by visiting Mr. Bingley, what is the reader's status and role among the characters?

The use of the word "all" suggests the reader is surprised as well. If so, before we can determine the status or role of the reader we must understand that two passages in Chapter 2 make it clear who is surprised and who knows about Mr. Bennet's little trick. The questions to address are "Who was surprised?" and "What is the reader's status/ role?"

The first passage is:
Mr. Bennet was among the earliest of those who waited on Mr. Bingley. He had always intended to visit him, though to the last always assuring his wife that he should not go; and till the evening after the visit was paid she had no knowledge of it.

The second is:
The astonishment of the ladies was just what he wished; that of Mrs. Bennet perhaps surpassing the rest; though, when the first tumult of joy was over, she began to declare that it was what she had expected all the while.

The first quoted passage makes it clear that the reader is not meant to be surprised. The narrator has told the reader precisely what Mr. Bennet has done and how. All surprise for the reader is eliminated from the situation by the narrator at the very start. The reader knows about Mr. Bennet's secret. The reader is knowledgeable about the joke Mr. Bennet is playing on his wife and daughters.

The second quoted passage makes it clear that Mrs. Bennet and the five Bennet girls are the ones who are surprised. Mr. Bennet's "sarcastic humour" and "caprice" has made them the objects of a little trick he has devised and played on them.

Mr. Bennet was so odd a mixture of quick parts, sarcastic humour, reserve, and caprice, that the experience of three-and-twenty years had been insufficient to make his wife understand his character.

Since the narrator has enveloped the ladies in situational irony (he says he won't, then acts as though he has) and dramatic irony (we know what they don't know), we are in a position to observe their surprise while knowing all along that Mr. Bennet did, in fact, go visit.

Therefore, the reader is not surprised; the Bennet ladies are surprised. The answer to "Who is surprised?" gives valuable clues to the status and role of the reader while contradicting the idea that the reader is surprised along with the Bennet ladies.

Status: The reader's status is almost equal to the narrator's: we are privileged to know things from the narrator that characters don't know.

Role: The reader's role is that of observer. The reader is not a participant: we do not feel what the other characters feel (neither Mr. Bennet nor the Bennet ladies) when they feel it. The reader's role includes being more knowledgeable than the characters.

Summary: The reader is not surprised. The reader has a privileged status having the narrator's confidence. The reader's role is that of observer, not participant.