[Aerkuld]

If you get the Carrera digital system you can program the cars to limit top speed so kids can drive them without crashing off the track all the time. You have the ability to change lanes too. You also have features such as running a few autonomous cars that the computer drives around at a constant speed. They change lanes at random too so can really liven things up.
Expensive initially, but you may find that the set has more future potential as your son gets older.