We have a Fantastic Fan in the center of our coach. I open the vent and run the fan on low. It seems to help in pulling the hot air out at the ceiling of the coach.
I know the OP asked about keeping passengers cold, but another poster talked about a curtain. Generally, it's just my wife and I when we travel. I took a spring loaded curtain rod and hung a clear plastic shower curtain on it. I install it just behind the front seats a few inches below the roof. It helps to keep the cab colder and has a center opening so my wife can get still get to the rear of the coach.
No matter what, we find that at about 3:00 pm during summer travel, we have to turn the roof A/C on. We try to turn it on about an hour before we stop so that the coach isn't unbearable as we pull into a campground to check in. We leave the gen and A/C running until we can hook to shore power.