To allow at least an appearance of "clean hands", I can see Harry & Daphne going after Ron; Hermione & Daphne going after Ginny; Harry & Hermione, possibly backstopped by Neville (and co.) going after Snape and Malfoy; and all three going after Dumbles. It's going to be quite the entertaining semester for everyone else.
Author's response
You're fairly close, but I'm not going to say how... Why spoil it?