Hi, I booked my trip through the Disneyworld website including my flight (Continental). I booked a late flight due to issues w/ DH's job but now we can leave on an earlier flight. So far I've paid only what was required of me to pay and my final payment is due in Oct. Can I change my departure to an earlier time without any fees incurred?

you bought the least expensive/most restricted tickets - so as others have said, unless the airline makes a major change to your flight time (or if it's AirTran and they've made any change, or if it's Southwest and you understand you'd be required to pay any difference in airfare), no, you can't change without incurring fees.