It might be a better idea to take him to the flying field to look around. There you will be better able to grasp the whole picture of rc airplanes. Plus you get to see them in action. Ask questions of the people as to what type of plane, motor, radio, and field equipment you will need. Last but most important is to find someone to help build the plane of choice, and learn how to fly it. For the most part, trying this by yourself is almost a sure crash.
Most trainer planes are similar in design (flat bottomed airfoil,lots of dihedral in the wing, and tricycle landing gear) and most radios are similar in function. The most important is to get a radio that matches the one the instructor has. (the different brands usually are not compatible) Hope this helps, Loren