That was the advice I was going to give you so I am glad to hear night 1 was successful! You could also try a chart where in the morning everytime he has slept in his own bed all night then he gets a sticker or a check mark and after so many (you decide the magic number because only you know your child best) in a row he gets a reward. His reward can be anything you know he would want to work for. Some examples.....treats, his favorite dinner, having a friend come for a playdate, trip to the zoo or other exciting place he likes, shopping for an item at his favorite store again you know your son best so what ever you are comfortable with.
Our children grow so fast but there are things we have to do to help them grow up because I don't know about you but I would NOT want a teenager crawling into bed with me every night! LOL!!!