G.B.
Stop limiting his fluids. This makes his urine stronger and there is less in the bladder. He might actually wake up to go pee if he could feel the urge. Since there's not much there he doesn't really feel it and wake up.
It may be a couple more years before he stays dry at night so I'd make sure he completely understood that he is not to leave his room except to go to the bathroom and change. Then he has to go back to his bedroom. This way if he's up and doesn't want to go back to sleep then he needs to stay in his room and play.
If you have a baby monitor you could set it up in a hallway so any noise will let you know he's up. Then you can cat nap until you're ready to wake up for the day.