going to be a HUGE surprise, because we are very protective. But if he can't go fast on something he's going to implode. And as a parent you choose your battles...
Just saw this- probably better to get on the 150F- it'll be non-violent enough to keep him safe until he can prove himself. Then it becomes your 14 yo's bike and Captain can get on a 125 2 stroke or 250 four stroke.
You are probably really, really confused about the interchangeable terms on power.....
Basically- any air cooled 4 stroke (like the 150 you are considering)- those have the fins all around the motor- are good entry level units fast enough to be fun, but not too fast to do 150' jumps.
Any water cooled bike- has a radiator just like your car- are violent and are meant to be. They need to be fast to win races, do big jumps, and generally cause lots of mischeif, mayhem, and ultimately fun. The two strokes, by their design, are more power dense...that means a smaller 2 stroke motor will make the same power as a bigger water cooled 4 stroke.
In dirt bike world, that is accepted as a 125 2 stroke is equivalent to a 250 four stroke and a 250 2 stroke is equivalent to a 450 four stroke.
A 2 stroke requires you to mix the gas and oil like your weedeater. A four stroke requires you to change the oil periodically.