My 5 year old reads 3 books before bed every night, usually science books. She is weird.
I use to have a strict bedtime routine, but I've thrown that out. We shower if dirty, get dressed, do our teeth, potty, and then read a book. It's rarely in any habitual order. We've mostly stopped reading to our 5 year old. She usually prefers to just read to herself.
With baby, I change diaper, sleep sack her, read a quick cloth book, and then let her nurse. I then put on her noise machine and put her in bed. She usually just rolls over and puts her thumb in her mouth. Tonight she babbled to herself for about 10 minutes. She also got a bath tonight, but I only give her a bath twice a week (my oldest got one every night!)
My middle child can sleep anywhere and through anything, just as long as he has his stuffed animal friend. He is usually asleep within minutes of hitting the pillow. He likes his sleep, and always has. In fact, one of my favorite memories is of him giving my mom his sleep sack at 9 or 10 months old because he wanted a nap!
I don't have any suggestions as to what you can tell your son when he can't just fall asleep. Does he have any ideas?