Is there any kind of bribery that would work? Like if you said "If you stay quietly in your room by yourself and go to sleep tonight, you can have xyz in the morning". My sister used this tactic with her DS, she would have a brand new toy/game, put it in his room so he could see it and tell him he could have it in the morning if he was quiet and went to sleep. It worked really well .

Otherwise is there some kind of irresistible toy that you could give to him just for bedtime? You could tell him it is for bedtime only and he can play quietly with it if he stays in bed by himself?

I hope you find something that works .