I would speak with a banker at your local branch about the account. Even if they don't have a way to extend the closure date they can give you an idea on the process for repayment and the close out fee. If you had overdraft fees you can ask for courtesy refunds BEFORE it closes so the balance plus your closure fee are not so high.

A charged off account won't report to chexsystem right away and you already have another account so you should be fine. I have seen clients charge off and pay it back within a week and open a new account with the same bank without issue. Of course each bank is different so ymmv.