We went with a 26 month old in January, and she needed a 2 hour nap everyday. We went back to the hotel, and, including travel time, it was closer to 4 hours. She slept in a pack n play from the hotel, and it was fine. She never falls asleep in her stroller and rarely falls asleep in the car (even on a 3 hour car trip, she might fall asleep for only 30-45 minutes when she usually takes 1.5 to 2 hour naps). I think that you just have to know how your child is.
If your DS won't sleep in a PNP, I'd try renting a crib. Everyone will just be more comfortable and rested, and he will be safe. This one is mentioned here often...
http://www.abbf.com/ I took their phone number with me in case we had a problem (if she wouldn't sleep in the PNP or our stroller broke, etc.), but I didn't use them.
If you find that you don't want to go back to the resort one afternoon, you could just power through an afternoon and see if he falls asleep and naps in the stroller. If he didn't, you could always go back to the resort.
I wish that we had powered through an afternoon just to see how it went, but our DD6 also napped nearly every day!
I think that part of the problem is that even if they do fall asleep in the stroller, the nap is much shorter than if they are in bed. And the other part is that when they finally do fall asleep, it might be much later than when they need it (and in the middle of dinner). Again, it depends on the child.
To me, it boils down to knowing your child (if he falls asleep anywhere easily or not) and being flexible with your plans.