Continued from last post......To cut a long story short the best keyboard to get is a Yamaha one. Maybe a PSR-75 or around that number. What tends to happen is that they make models of PSR-75 then PSR-85 and then 10 years later then go back to PSR 76, PSR-89 etc. So the number is little indication of how old the keyboard is. PSR-75 keyboards tend to have 49 keys, I think this is sufficient for an absolute beginner, particularly if you are unsure if your son will stick to playing the keyboard. When the numbers eg PSR get to around 200, then these keyboards have around 61 keys. this is the biggest you will find on a keyboard. 88 keys i would say is more like a portable piano and far too big for a beginner.
If your son is really determined and is keen on the idea after a short time then I suggest he takes up piano (not keyboard) lessons as this will train his fingers better and improve coordination. If you can play piano the keyboard is a doddle. I would always encourage someone to learn to play the piano and not the keyboard if they really want to do well. its like guitar. if you learn on an electric and then you try to play an acoustic your fingers are not trained for the hard strings on an acoustic. its the same with a piano, the keys are much more weighted.