All of these suggestions are good...
I was his age when I had mine removed, all 4 impacted as well, and I was one of the lucky ones that didn't experience any side effects, once the gas wore off (it made me cry. Not giggly, not chatty, just sobbed the whole way home. My poor mother.) No prescription pain meds, just Tylenol. Lots of mushy comfort foods (mac-n-cheese, mashed potatoes, soups, ice cream) I was back in school after one day. I hope it's the same for him! (Well, except for the crying part.)