We have a VERY hard time doing rope drop for the first week in Orlando. It doesn't matter how exhausted we are, we can't go to sleep until our bodies' bedtime (we start bedtime at 9 just for DS) and that doesn't help us get to sleep nice and early. And no matter if we can go to bed early, waking up in time to be at the turnstiles for an 8am opening is just too hard for us.
If you won't be napping, why take breaks? That's just adding tons of travel time for not much bonus. If you'll end up swimming, recognize that it might very well exhaust everyone (or sunburn everyone).
OH gosh I just saw you're doing a redeye. Yeah, I don't know. Those don't work for *me*, let alone for my son. Let alone for when he was 4. If you have kids like my kid, I give you all the hugs right now, because my kid falls to sleep for an hour on a plane, wakes in a miserable panic and won't stay quiet, then passes back out, wakes up an hour later, panicking, etc. He does NOT do this at home. It's the plane, the dehydration of a plane, sitting up, etc... Flying from Vancouver to Heathrow we got approximately 20 MINUTES of sleep the whole flight. It was a joy. I really hope you have a better experience than we have while flying during sleeping time. The 4 year old will be the wildcard for staying up.
And remember you almost certainly will not have a room, and aren't supposed to until after 3pm, so if people are miserable, plan on pool time or something. Sunscreen and swimsuits need to be in the carryons, absolutely.
I wouldn't plan, under any circumstances, on entering LATE afternoon, though. The excitement of disney will get you up earlier than that!
