At home, my kids get up relatively early and go to bed early. At WDW, who knows????? They can stay up FOREVER.
Honestly, my BEST traveler last time was my 2yo!!! The 4, 6, and 8 yo's were melting down, but he was going strong at 10:00 one night waiting for the bus to POP after fireworks.
I think vacation is a weird time. It's hard to predict what your kids will do. Build in breaks and down time and don't get too upset if you have to miss something you have planned.
If you have something really special like Cindy's or HDD or something, plan around that and make sure they are rested. Otherwise, you really never know.
On our last trip, we planned to go back and take naps, but my little ones were troopers! They didn't need to sleep, so we pushed on through most days. We had "extra" time that we didn't plan on, so we were able to take it easy mid-day and see things that weren't on the schedule.
If there is something you REALLY want to do at night, plan an easy day the NEXT day. They will be tired.
It's so hard to plan, so don't try to do something you have your heart set on when you also plan a full day.
jmho!!
-Barb