Don't fret. You might actually be able to get those other flights after all, and not pay any change fees. Although I can't be 100% sure because it is a date change. This is what happened to us last year.
We wanted an nice 1pm flight home, but when the flights were released, the 9pm was $59 and the 1pm was like $99. So we booked the 9pm ($40 x 6 people, is a lot of money).
A few months later they changed the time of our 9pm flight to 9:45. We called them, and they have a policy that says if they change the flight, they will let you change without the fee. We said we had time constraints and could not leave that late, and they put us on the 7pm. A bit after that the 7pm became 8pm, so we called again with the same that is now too late for us story. And guess what, the only earlier flight in the day with seats was the 1pm! (which was now $189 to book). So we got our 1pm flight for the $59.
As everyone says about AirTran, they are known for changing their times. So if they change the time of yours, maybe you can explain that this time change is not doable for you, and see if they will let you change to this other date.