At this point in time, you have no choice: OSX cannot legally be run on anything except Apple hardware and cannot be virtualized (except for OSX server.) So if your son need to run an OSX version of something, then the only legal way to do that is with a Mac. But the real reason I'd highly recommend a Mac for your son is because graphics performance in a virtual machine is not very good yet. So for all the graphics intensive programs your son needs, it will probably be extremely painful for him. Best to just get a Mac. Don't get me wrong. It's not that it's impossible. Since you have Workstation, you can try it for yourself with PC versions of Photoshop and the like. But schoolwork, deadlines, teacher's notes don't match since you're on a PC, etc. I think your son can do without that extra stress. 
That said, for Mac notebooks, there's only two choice. Macbook (13") and Macbook Pro (15", 17" and Hi-res 17"). If you need the biggest screen, then your only choice is 17" Macbook Pro. The hi-res 17" fits more pixels, but obviouly everything is smaller on screen (and is more expensive.) Performance on the Macbook is slightly slower than the Pro anyway. A good compromise might be the standard 15" or 17" and get an external monitor. That's what I do with my 15" MBP. When it gets to my desk, the external monitor and Firewire hard drive (for Time Machine backups) get attached.
The MBPs come standard with 2GB of RAM. I'd consider bumping that to the maximum 4GB since it's a lot of Adobe software. You can get the DIMMs much cheaper online, (It's just 3 screws to replace the DIMMs on a current MBP, unlike the previous models.) And with VMWare Fusion, he can use that extra memory to run Windows and Linux virtual machines.