night mares with night sweats

VernWorried, nightmares are sometimes caused by stress as our dreams are the brain's way of making sense of what's happened and the information we've processed during the day.
Ask your grandson if keeping a sleep journal might help - get him to record his activity, stresses, sleepiness, and what the dreams are about if he can remember. Some people find their diet plays a role in dreams (there's an old wives' tale about cheese causing nightmares) so perhaps keeping an eye on whether he has nightmares after certain foods might help too.
The sweats may be related to thrashing about during a nightmare or may be cause by something else. There are all sorts of scary things that cause night sweats (infections like TB, cancer), some meds he's taking, having an overactive thyroid or having a blood sugar dip if your grandson has diabetes.
The most common cause is simply being too hot at night. he should make sure his bedroom is the right temperature and that his bed coverings are the right weight for the weather/season.
Another cause of sweating is 'idiopathic hyperhidrosis' which means 'sweating from an unknown cause'. This usually comes with some daytime sweating too so isn't limited to just night sweats.
If you or your grandson are worried, or the info above doesn't help then talk to a doctor to ease your mind(s).
Good luck.

Have you found a solution for your son's problem yet? I have the same symptoms. I am doing sports as well and I have been going through nightmares and night sweats for such a long time. I had always thought it was stress related until I had an glucose tolerance test so I found out I have hypoglycemia. He may have it as well. He should see a doctor.