I agree with the refundable ticket route. Go to Delta.com, buy a refundable, full-fare ticket to somewhere not too far away for an hour or two after your brother's departure time (pick an Airtran market - that's likely to be cheap), check in online and you're good to go. Meet the brother and his wife and baby, and then change your mind about your refundable flight. Don't board - since you decided to skip the trip. Seek refund online or call or start process in person (whichever is easiest with DL in ATL).