Ric,
You're very lucky that your son wants to do the flying thing. I have an 11 year old thats kind of hohum about it all. I have 12 models of all kinds and sizes and he just isn't impressed at all. He just wants to skate board all day long. I don't get the skate board thing but I don't discourage it. At least he is not getting in trouble somewhere else. Ironically, I just soloed a 12 year old neighbor that can't stop calling me to fly on the weekend. I can't say no to him because if you saw the look on his face when he finally soloed you'd have to have a heart of titanium to say no. He is one happy kid. Its the kind of enthusiasum that comes with a life long commitment to the hobby. But my wife is giving me grief for not spending time with my son and not the neighbor's. I refuse to push him into something he doesn't want. Only time will tell, I guess.
Money is always a tough one. My problem is time. So, unless your son has shown good skills and confidence don't spend in the $1000's. What does presenting well mean??? I would try to get something used. Look on the ads in RCU. There lots to choose from. I'm not an IMAC guy, but Dave Patrick has a small selection but makes good quality ARFs. RCshowcase sells good engines. Servo City and Radio South sells good electronics. Most of all they dispense great advice and support. Good Luck and enjoy every minute with your son.