I have a bit of a problem with the fact that my son's daycare (he'll be 3 in November) don't have napping in a separate room - so the children that don't nap (or whose parents don't want them to) are in the same room as those napping.
My son isn't doing full days there yet but this will become an issue when he does, in a month or so's time. Frustratingly, when I chose this nursery it was one of the crucial things I asked, and at the time they did nap in separate rooms. But their policy has changed on this and it's only recently I have found this out.
I know from past experience at a previous nursery that he will refuse to go down if he sees other children playing... yet he needs his naps so much - he naps up to three hours in an afternoon and still goes down to sleep at 7.30pm. (I know he won't get to nap three hours at daycare but even an hour or so will help stop him falling asleep in his dinner come evening time)
I've made appointments to see others so that I can compare and contrast the nursery he's at with the others out there, as I feel so strongly about this I may move him if necessary. However, maybe I'm being unrealistic: your own experiences would be very useful!
I worked in a nursery and we used to allow old children to sleep on bean bags in the corner of the room if they wanted to nap. This was because we didnt enough staff to supervise sleeping children in a seperate room.
Do they have a baby room? Most baby rooms should have a sleeping area for babies that is supervised. Maybe ask if he could nap there?