D.,
Having one's Wisdom Teeth removed can be a brutal surgery, with a lot of bruising, soreness afterward, etc.
However, it is usual that the oral surgeon recommend removing all four of them at the same time, then your son only has to go through this surgery once, and its done and overwith.
Most oral surgeons will administer a general anesthetic, rather than a local, such as novacaine, if you request it. You may have to pay extra for it, if your dental plan doesn't cover general anesthesia for dental work, but whatever the price, it is worth it, as it will make the surgery much easier on your son.
Wisdom teeth are always problematic, and, in most cases, all of them need to be removed, eventually, so it makes sense to have the surgeon remove all of them at once to begin with. They often come in sideways, under other teeth, or emerge in such a way that they crowd the roots of other teeth, which can cause pain, and even cause problems with your son's normal teeth as he gets older.
Also, Wisdom teeth are usually quite brittle, and decay easily. The roots on most of them are huge, and trying to extract them, once they are decayed, usually causes them to break off, which will make it much more difficult to extract them from the jawbone. Removing them before a problem begins is a good way to prevent an abscess in your son's mouth, or the movement of other back teeth which may present a problem for him as he gets older.
Hope this information helps, and once it's done, I wish your son a speedy recovery!
D.