We tried once with DS when he was 2.... Definite failure for us. He fell asleep during Illuminations...we walked back to BC. He woke up, wouldn't go back to sleep. Next morning still got up at normal time.....worst mood and day for us ever.
Ten years later, we tried with DD this past trip at 20 months old ....aweful! It was her 6 th trip, and we hadn't tried staying up past her normal bedtime. We were there with visiting family though, who may not be back. Pretty much same routine.....she fell asleep, woke on monorail going back to Poly. I finally got her to bed by 1 am. She was up by 5 am the next morning, super cranky....not a fun day for any of us!
I have learned my lesson! We cannot do late nights with my kids, sticking to bedtime is important for us to have a good trip. Have a fun trip, hope all goes well!