I have already transferred my BTC to an offline wallet (my Trezor) . . .
I'm now thinking to sell my Altcoins and doing the same to protect my BTC and collect free BCC.
What is everyone else doing with their Altcoins prior to 1st August?
For altcoin i think it's not a problem, Which must be considered is Bitcoin. Your step is correct save Bitcoin in offline wallet to avoid the risk of loss.
I think saving altcoin in Wallet is not problem.