We will see Mr. Collins.
In canon, Mr. Bennet ignores the letter and springs it on his wife but I can't see my Mr. B doing that. I have a few scenarios rolling around in my head. The leader right now is that he gets the letter, invites guests to fill Longbourn, and then replies to Mr. C that 'the inn is full'. Of course, Mr. C being a bumbling imbecile, assumes it's a mistake and shows up anyway. Depending on who I decide to fill Longbourn with, they will have fun informing him of the two coming babes and that they have no need of his charity.
I do have a while to decide. The letter in canon was dated October 15th, which is after the assembly, so it will be at least a chapter before I have to make a decision.
