I recommend getting a bed wetting alarm that should wake your child up when the alarm detects some urine.
You place the bed wetting alarm sensor in the child's underwear and when they pee on it the sensor detects the wetness and turns the alarm on which usually wakes the child up if they're not a sound sleeper.
If you take your child to the doctor they can prescribe some nasal spray or even pills that can help slow down the production of your child's urine which will help them to stop wetting the bed.