There's nothing you have to fix. You are entitled to the additional $2,200. That's the way the stimulus payments work. The simplest thing to do is just leave it the way it is and accept the extra money.
If you really feel bad about taking the money, when TurboTax asks how much you received for each stimulus payment you could add the amount for the children and say that you received more than you actually did. That will eliminate the credit on your tax return. But the IRS might correct it and send you the extra $2,200 anyway. I don't know if they'll do that, but they know how much they sent you. Again, the simplest thing is to just take the extra money.
