The D5000 is very close to the D90 in power, has the cool swivel screen, and includes D-Movie mode. For the money, it's one of the best values around. Good choice!
The longer the lens, the more VR is needed. You might consider the 18-105mm Nikkor. My wife uses it, and it's very sharp, has VR, and is a wide-angle to short telephoto. Not quite as long as the second lens, but a lot more convenient. You can buy DEMO (usually refurb) versions for less than $300 USD. I bought one for my wife for merely $274 and it is excellent for the price.
Oh, also check out Mastering the Nikon D5000 for your son. This NikoniansPress book will help him through the steeper learning curve for the full-featured camera.
============================================== Darrell Young (DigitalDarrell) www.pictureandpen.com "Better too many words than not enough understanding." ==============================================