My Wife saw a photo somewhere on pinterest of a Lightning McQueen cut-out of plywood that the kids could change the tires...and well...here is our plywood McQueen complete with changeable tires.
I had a leftover piece of meranti plywood from a parade float lying around that we were using to shoot hockey balls at instead of denting up the wall.
The image I used as my guide, to draw McQueen, was taken at an angle so I skewed the image back to "side on" as best I could (you can see the reference image on the plywood in the above photo.) The plywood was previously cut to 4x6. We wanted something that was taller than most of the kids so I stretched the proportions of the photo so that when scaled up to size it would fill as much of the plywood as possible.
I put one bolt in the centre of the tire, counter sunk the bolt in a piece of leftover flooring and set in place with automotive glue.