Yes, WHIZZBANG is a Scrabble word!

Letter values in Scrabble US: W 4, H 4, I 1, Z 10, Z 10, B 3, A 1, N 1, G 2.

Is it a valid word?

WHIZZBANG is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a small high-velocity shell; it makes a whizzing sound followed by a bang when it hits
a firecracker that (like the whizbang shell) makes a whizzing sound followed by a loud explosion

Also: whizbang shell.