From my knowledge personal wallet associated with an exchange is actually holding there... not in your wallet. But not sure about that, you better find out in what conditions you are with that wallet to be sure.
Initialy, i heard it could work only on personal wallets, but now i see bittrex and kraken said they will double it for everyone who has some bitcoin amount there.
Coinbase, don't. So search for places you store your bitcoin to see details.
Although, who knows what joke it is with that thing... doubling money... huh :-). Isn't it sound to good to be true? hehe
RE: Kraken supports BCC!