If you find both of you are very interested, as someone already suggested, go out and buy a nice kit and build it with your son to teach you and him the basics that will prove usefull later. I would suggest a glow engine plane from a .40 to a .80 maybe even a scale. You might not be ready to fly it for a number of months but you will have fun putting it together and it will make a nice show peice, i know i have made a number of scale planes that look awesome just sitting on the table. Scale WWII birds is my addiction. Nice kits range from about 150-300 for decent ones then of course an engine but you wont need that until you are ready to fly it. But once you are ready to take it out, it gives you a certain amount of pride to see something you built lift up off the ground and smoothly climb. Definetly more satisfaction than a pre-built model. Also, i know you want to go electric because of the price, but just as i write this, a couple of glow engine planes, a .25 texan full built with everything including a controller is going for $200-$300. So keep your options open.
I have seen other really nice ones go on ebay too for about 300 with everything. Thats how i personally started.