Dagosa and jtsanders,
I have a PT Cruiser with heavy tint on the windows. I tried turning off the side vents and pointing the center vents directly to the back of the car, then tried pointing them upwards (hoping the air would richochet off the roof). It helped, but not enough. With two seats, there’s no real way of getting air to both sides of the car, especially to the rear facing seat.
We thought about a Jetta SE because models prior to 2011 had a backseat vent that came out of the center… unfortunately, they discontinued that feature in the 2011 redesign. 
I’ve looked at 3rd row options but I would love to avoid a car that big…
Caddyman, The American Association of Pediatrics and Texas law disagrees with you. I’m not going to risk going against what my pediatrician says, not to mention do something illegal.