> Are there any issues with the the spray water from the car wash
> entering the rear air grills?

There is a NEGATIVE to having water enter the rear side air vents.
There is a horizontal shelf in behind the rear tail-lights that will hold
water and promote rust out the shelf and seam rust.

One good opportunity for Canadians (& those Americans close to the
border) is Krown Rust Inhibitor.  Be sure to get your van done yearly!!

Malcolm