When opportunity knocks, you have to open the door, but be ready for what comes in. Plan on being busier, as it is anyway the day before Thanksgiving. Any of his customers that try you out while he is closed won’t come back if you aren’t on top of your game.
Maybe offer a special deal to those new customers, like honor his coupons plus an extra buck off during those two weeks.
Then reap the rewards long after he opens back up.