Thanks Ladies. All great suggestions!!
I just wanted to note that he just turned 4 on December 8th so prior to this he's always napped. I think his preschool class does nap but he's in the 3-4 yr old room so there are lots of 3yr olds in there too.
On days that he doesn't nap, he's an absolute monster usually. And he never sleeps any better. There are rare occasions that we can get him in bed before 8 and he will sleep until 6:30 but it's really really rare.
We do have a nite light in his room too.. and a ceiling fan that gets turned on. I also have a floor fan that I leave in the hallway. (for mommy because daddy snores but also to drown out any noise for DS).
Where did you find the blue moon/yellow sun light? That might really work for him.