My daughter didn't nap every day. She napped in the stroller a couple of times and that worked very well. She slept while we walked around and saw things we wanted to see, and then was ready for more when she woke again.
Our first day was at Epcot - the kids napped right at lunchtime and we found a cool place to eat and recharge ourselves while they slept, and ended up staying all day, even though we'd planned to leave and return later (or hit another park later). But Epcot was a GREAT day for the kids (2yrs, 3yrs and 6 mos.), and it wasn't as crazy busy and stressful as Magic Kingdom. The worst days with the kids were at Magic Kingdom, and I think that's just b/c there is so much going on it wears them out more quickly. But they LOVED Epcot - the aquarium, Nemo ride, Turtle Talk with Crush, the Character Spot where they got to meet several characters, including Mickey, Pluto, Chip and Dale, etc., the boat ride in Mexico, Spaceship Earth - they loved all of that. But, at this age, they can enjoy any of the parks, especially if they're into characters and you take time for that.
My suggestion is NOT to have a set in stone idea of what you're going to do regarding naps, just have a plan and go in knowing that it might change. We had planned to leave for naps, but after day one, we decided to decide each day what was best. We left Magic Kingdom early on day two for napping, b/c it was just way too much for everyone, but then day 3 we thought we'd have to do that again and didn't - so I say, just go in with a plan for both ways and see what happens when you're there. All kids are different, and many factors (heat, crowds, sleep, etc) may play into your decision once you're there.
Have a great trip!