Waking children up during nightmares.
Is it a good idea to wake up a four-year old if they are having a nightmare?
It is never a good idea to wake up a child who is having a nightmare, normally the nightmare itself will wake them up. They often go back to sleep soon afterwards, so it is pointless to upset them even more by waking them up.
If they wake themselves up crying, you should certainly be there to reassure them and get them back off to sleep.