Making paper cars from templates can be fun, however kids get something from doing something all by themselves. With that I drew out these steps so the boys could create a paper car from nothing.
Find a rectangle around they can trace (if they are able drawing a rectangle is also good)
Trace 3 rectangles onto a sheet of paper
Trace the short lines on the end of the middle rectangle
Close these lines to make a box
Draw tabs on the outside rectangles (these tabs will be used to glue the paper car together)
Draw Wheels on the outside rectangles
Draw the car. The middle rectangle is the top, the outside rectangles are the sides and the squares make the front and back.
Cut out around the outside of the paper car
Fold the outside rectangles and squares down to make the car
Glue the tabs to the inside of the squares to hold the car together
Or you can print these templates