K.D.
An hour and a half is a very long time to expect someone who is not sleeping to lay there quietly in the dark -- even an adult. And 4 is long past the time when some kids give up naps. There should be more flexibility at the daycare. I mean, these are kids, not robots. He does need "down time" where he plays quietly. You need to talk to some other parents, then talk with the daycare to find out why they can't be flexible.