I don't usually nap, but I cannot sing the praises of mid-day breaks highly enough. Just find somewhere to sit down for a while in the air conditioning and talk with your companions about how the day has gone, plan the rest of the day, or just soak up the atmosphere. I tend to use the time to write in my travel journal since I mostly go solo.
The best part of breaking like this is that you don't have to go all the way back to your own room, if you're in a far-flung or off-site hotel. My favorite place to break from MK is the lobby of the Grand Floridian. It has beautiful decor, comfy couches, and live music (alternating piano and big-ish band). Grab a snack and drink from the quick-service location and you're set. I believe all of the Deluxe resorts have lobbies with comfy seating and somewhere nearby to grab a snack.