Jersey girl,
we really followed ds's cues for the daily schedule. DS sleeps very well in the stroller we brought, and I knew he would not do good to go all the way back to the hotel for a nap, even though he needed down time.
Generally speaking, we left the hotel as soon as he woke up (close to park opening). First thing in the parks we did what we really thought he would enjoy. Then, after about 2-3 hours, he would really just start looking tired and over-stimulated. This was always about lunchtime, so we would get a good lunch (whether it be ps or cs) and feed him. Then the guys (dh, my brother and my dad) would split off and go ride the 'adult' rides that make me sick. Mom and I would put ds in the stroller and start to wander around in 'less traveled' areas. DS would conk out almost immediately, and he would usually get a good hour nap(not as long as at home, but enough for him to get rested). We would meet back up with the guys then, maybe do 1 more thing for ds on the way out, but we would head back to the hotel. Then we could lay around the room, ds could play with his toys, and watch some cartoons, and enjoy some down time for an hour or so. THen we would go back out for dinner, whether it be back to the parks, dtd, chef mickey's, etc.
DS loved the night parade at MK and I would try to see that if you could. It started pouring 1/2way through it for us so we only saw 1/2 of it, but he really loved it. This was the only night we stayed in the parks late (about 9). One day we were at dtd until about 8:30, but the other nights we were back to the hotel by around 7:30. DS was always tired, but walking by the goofy fountains at POP made him want to swim, so we usually let him do that for 15-20 minutes before bed as it relaxed him and us (it was still warm then).
I have heard conflicting stories about the quality/condition of the car seats available through the rental agencies in orlando. I would bring my own even if you decide against the seat on the plane.
Also, I have heard alot of people saying that drinking really helps their ears on the take off/landing. so we brought some juiceboxes , as we didnt want to rely on the finding a stewardess if he got fussy. The juiceboxes worked good in the parks too, just to have something in the diaper bag. I would prefer milk, but the juice was great because it didnt require refridgeration. I would warn you to bring extra diapers if your ds isnt use to juice, ds gets very little at home and we found that things were moving pretty quickly through him with a juicebox a day
Hope that helps! We had a great time, but it was TOTALLY different than any trip without him. We have entered a whole new era in disney trips for awhile
