If your son is used to a dark room - why change it? Just a thought...
It took my son a couple weeks to adjust, but he doesn't get out of bed at all. When he wakes up in the AM he just calls our name or sort of plays in bed until we check on him. He only got out of bed right away in the beginning... but never in the middle of the night.
If you still feel that you need something, we plug in a night light behind the dresser... plenty of light, but not directly in his face. Or you could use one of those battery operated lights that you push on and off... you'd go through a lot of batteries, but they are not as bright. In fact, you could teach him to turn it on and off when needed. (They really are smart enough at that age.) And those just stick on the wall so you could put it where ever you want.
Good luck!