I would have your friend come by to feed them every other day if possible but feeding them right before and right after will probably be fine as long as they are getting enough water from the mistking.
The temp drop should be fine. What's your outdoor setup like? Do they have plenty of coverage to hide from the heat at the height of the day? I've heard stories of people's chameleons frying in the sun on a hot day. I'd be more concerned about that than the night drop. I live in SoCal also. What month is your trip in?