Last year our flight left at 6am out of DTW. My dd turned 3 during the trip and the youngest was 10 months old. (+ a 11 & 12 yr old) We live 1 hour from the airport. It was a tad stressful just because we had to get them up at 2:30am. I left them in their pajama's. We landed in Tampa right before 9am and headed over to the Tampa zoo b/c we were able to use our zoo membership there. I just changed them in the parking lot to shorts. (We went in Feb. and it was freezing in Ohio, which is why I left them in pj's. The older two of course were dressed.). By the time were done we drove to Orlando and checked in.
We leave in 4 days for our next trip

and we again picked a 6am flight (so it couldn't have been that bad, right?! LOL). I wasn't looking forward to it. Nice thing the airline actually changed our flight departure time to 9:45am about a month ago! So it worked out in the long run.
Have fun ... you will all do fine on the early flight! I look at it as getting to Disney faster.