Oh, so they'll soon be in Hogwarts! What is this suspense with Dean's note?

Was he attacked or something?
I must say, I haven't quite visualized how Harry would tell his friends about the prophecy. Your take has Ron acting in character. It's quite plausible for Hermione to use logic in evaluating the prophecy.
As for Trelawney's old prophecy of Voldie's faithful servant? I gotta admit, I've always presumed she was referring to Wormtail.
The "birth and death parchment" is an interesting concept. That was a good explanation too as to why the MoM didn't publicize Sirius' death. Or maybe you plan to have Sirius back later on? Don't tell me if you do.
I chuckled at Harry noticing how Ginny has grown. Good to know he acts like a normal teenager at times, especially when it comes to noticing girls.
>>Remus: ...if you showed him how to use it, Nymphadora
Tonks: And I forbid you AGAIN to call me by that hideous name
=>Heehee!
My con crits for this chapter would be about its length and dialogue. I find it rather long. Or maybe it's just my slight headache?
Some of the teenagers spoke very formal English. Example:
Some dialogue sounded too formal for teenagers, though. Examples:
Ron: "I'd love to be able to perform magic outside Hogwarts."
=>This could be restated as "Wouldn't it be fab (or cool) to do magic outside Hogwarts?"
Ron: "Besides that, the Weasleys' Wizard Wheezes is going really well. Our household income has increased a lot with the twins' business. ..."
=>"Weasleys' Wizard Wheezes" is quite a tongue twister. It would have been more natural for Ron (or most people) to refer to it as simply, "the Twins' business", "3W", or "Fred & George's business".
The "household income" bit also sounded too formal.
Just my 0.02,
Pen