In this case, i would also recommend to take the train into Amsterdam. When exiting customs, follow the signs for the trains. Tickets can be bought at the machines at Schiphol Plaza, then go down to the platform where the next train for Amsterdam Centraal leaves from. Obviously, your son doesn't have that much time, so first thing i would do after arriving at Amsterdam Centraal Station is heading to one of the canal cruise companies in front of the station and take the next available general canal cruise. They last usually 1 hr - 1 hr 15 mins, and give you an excellent tour of downtown Amsterdam for a very reasonable price. For a first time visitor to Amsterdam, even if wanting DIY, a canal cruise is a must. There are quite a few companies competing but that should not be an issue. Take the first one you see. Afterwards, there would be time to wander around a bit in the old town and have lunch, then back on the train to the airport