How should I orient the laminate flooring in this room?
Not an expert but I have installed laminate in 3 rooms in my house.  I would go with the light (assuming you mean windows being the light source) rule for the following reasons:


Assuming your drawing is to scale, if you eliminate the alcove in front of the closet, the room is almost square making the longest wall rule almost irrelevant.
The reflection off the floor from outside light when you walk into a room will be broken by seams in the laminate (I've found that even the flattest laminate still has seams) which will make your room seem darker and probably look smaller as well.


Also, no matter what the choice, I would probably recommend putting the laminate in the closets the same direction as the main room.  I believe those rooms are small enough that the longest wall rule doesn't really apply and I believe it will look funny having the boards a different direction when finished.