1) It's tempting, but honestly, by the time I got to my room and checked in, I'd be so tired I wouldn't want to go anywhere. (That's me - air travel takes a lot out of me).
2) I don't know how long your flight would be, but even a 7:30 flight into Orlando isn't going to give you a full day at Disney. By the time you get off the plane, collect your luggage, get to your hotel (don't know where you're staying, either, which could be a factor), etc, it's going to be at least mid-day. If you planned on using that day to go to the parks, by the time you get to one, it might be 1, 2, even 3:00 PM in the afternoon, and you'll have been up since 4:00 AM or so. I don't tend to sleep well on flights, so I know that by the time the afternoon comes around, I'd be wanting a mega-nap.
3) This is why I always fly with Southwest. Free bags, and the key: free flight changes. 100% free. You only pay an upgrade fee if the flight you want to switch to costs more than the one you already payed for. And you're allowed to cancel any flight at any fare, but you don't get a refund - the money is credited as travel credit that can only be used by YOU specifically, and it expires after 1 year from the initial payment date. All that being said, Southwest has given me so much flexibility in the past in this regard, I can't even imagine any other airline. Not to mention that their prices are usually in line with all other airlines, if not less. That combined with free changes and free bags... Southwest all the way for me.
Consclusion: If it were me? I'd just sleep in and take my scheduled flight. Roll out of bed late, eat a nice meal, make sure you're all packed and have everything you need, cruise on over to the airport. Get on your late flight, get to your hotel, and relax. Grab some late dinner, and zonk out. Getting up at 3-4 in the morning to make sure I'm out the door by 5... By the time I got off that flight and into my hotel room, I'd need to chill and prepare for the days ahead.
Again, that's me. I'd be dead after getting up before sunrise and traveling and everything. I'd be zombie if I tried to accomplish anything that afternoon/night.