This year there is a 10-day break imposed in the NCAA summer evaluation period, which will start July 15 and run through July 24. During this period there will be no coaches at any events. 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. 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.
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.