I don't have personal knowledge on this. However, if I were you, I would ask the adoption agency first and see how they proceed with such issues. I would also check with the airline, maybe PR department or something, and see what they could help with this sort of possible-last-minute-change situation.

When buying tickets, I would either buy one-way ticket or get myself one-way award, when change-of-schedule is expected, so I wouldn't have to worry about change fee. It's possible to find good fare on 1-way ticket nowadays. Some airlines offer half mileage redemption for 1-way award tickets as well.

Which airline do you have elite status on? If you have a high enough status, change fee may be waived.

Good luck!