I really like the way you are handling this. Harry is intelligent and capable, and handles himself well. The others seems to be themselves, but they've really just been introduced, so you have time to add your own flavor.
As for the animagus forms:
Ron: Irritable, aggressive, quick to anger, and ferocious in a fight. Ron is a Wolverine.
Hermione: Smart, freedom-loving, deep as the ocean, willing to help anyone who is drowning in the sea of homework. Hermione is a Dolphin.
Ginny: Flighty, Fiery, intense, tiny, and as at home in the air as Harry is. Ginny is a Merlin. (A tiny falcon)
Neville: The other possibility for TBWL (granting him the potential as Harry, as the prophecy could not have known who Voldie would pick), slow to anger, but incredibly strong and powerful when he is. Neville's first form is a Kodiak Bear. He is also a calm, gentle healer, and a source of wisdom for his friends. Neville is also Snake.
Tracey: Smart, cunning, (and since she is apparently going to be an ally here, I'll improvise) prankster, wicked sense of humor. Tracey is a Coyote.
Blaise: Cool, composed, deadly, stealthy, competent. Blaise is a Black Jaguar.