Would it help to give my child less to drink after dinner and help him wake up at night to go to the toilet?

Both usually work very counterproductive and unfortunately contribute to further underdevelopment of the urinary system. Although it is advisable not to drink coffee, tea, chocolate milk or carbonated drinks after supper/dinner. Actually, we do not advise you to wake your child at night to go to the toilet. Your child needs to learn to wake up himself having a full bladder. That will usually not be the case when you let him wake up to go to the toilet.