My younger 2 both napped in the stroller (never attempted it with my oldest). With my middle DD, I was certain she'd never nap in a stroller, she always napped in her crib at the same time every day and I was adamant about keeping her to the same schedule in WDW. Yeah, right! Our first day there, she was wiped out an hour or so before her nap time and fell asleep in the stroller while DH was taking her back to the resort. Of course as soon as they returned to the room she was wide awake, wired and wasn't about to go to sleep.
After that, we just let her nap when and where she wanted...usually she fell asleep during 'down time' when there was no action...waiting for parades, shows, PSs. Other times we'd notice her getting sleepy and one of us would find a quiet shady spot and let her sleep there. Most of the time she'd catnap, once in a while she'd sleep for longer stretches. We let her do her thing and it worked out great for all of us since we normally don't like to leave the parks until dinnertime.
With my youngest, we didn't even attempt to go back to the resort for a nap and that worked out well for her too. I guess it really depends on the child, but even though my kids were always on a routine at home it just seemed to fly out the window on vacation. I can't imagine any of them napping on schedule at WDW. Plenty of kids do, but it just worked much better for us to play it by ear. And I am happy to say that in 5 family trips, we have NEVER had a meltdown or tantrum at WDW! Oh, wow, I hope I didn't just jinx myself!