I have a 2010 987.2S and it is an absolute blast to drive. 90% of my time driving it is on the track, and the car already came with loads of track related goodies like BRZ RS-one coilover suspension, GT3 front brake cooling ducts...etc. I also have the Sport Chrono package.
The biggest upgrade that I did was to replace the open differential with a true mechanical OS Giken Porsche G87 Limited Slip Differential. I highly recommend that upgrade, especially if your son will do any track or autocross events with it.
The 987.2 cars are the sweet spot for the Caymans/Boxster. There's a thread over on the Cayman / Boxster forums from a couple of months ago that has some good information to help with you & your son's decision:
http://forums.pelicanparts.com/boxster-cayman-forum/1092559-cayman-selection.html
Just note: the 987.2 cars are getting to be hard to come by. They were only made from 2009 to 2012, when there was a slump in Porsche car sales. Although the 718's are amazing cars, most folks haven't warmed up to the idea of a 4 cyl turbo Cayman. (Just wait until the all-electric ones are made...). Plus even the 981 Caymans / Boxsters are aluminum bodied - which can be pricey to "unbend" should something go sideways.
My mechanic informed me about a month ago that I could sell my 987.2 right now for 150% of what I bought it for last November. But -- what would I replace it with???