If your nephew will be around, he ought to either be playing with his high school team at a tournament or summer league, or he might want to consider one of the East Coast camp options like Five Star or Eastern Invitational. There are various camps that take place during the Big Time, and thereafter, but it all depends on what your nephew is trying to accomplish with a camp. No coaches out, and from CIF rules, no high school coaches working with players either during the month of August. If your nephew doesn't want to go back east for one of the August Five Star or Eastern Invitational sessions, then the second session of Snow Valley is a great idea. Snow Valley is a camp which is based on work.
Players get up at or before dawn to work on their games.
There's always a clinic, skill session or something going on where they can improve. Good luck to your nephew. Summer and the camps can be a pricey proposition, and not everyone can afford to send a player to everything that's available during the summer. If you need to make economic choices, or have other commitments during the July-August period, then that will shape your decisions somewhat. If it's just the former and you are limited by time or money, then pick Snow Valley.