That looks fine, missing some stuff like a wireless card (they're cheap, but silly not to spec it in...); you might want to upgrade the fan and box /cooling system if your son plays stuff like Assassin's Creed/Battlefield for long periods.
The processor is certainly good, but overkill, imho; doubt you'd see any real world increases/advantages over the i5 9600k playing games. The GPU is also on the upper end, but for gaming that's not a bad area for over-speccing.
I should imagine the Alienware brand does carry some prestige for your youngster - could always ask him... There are a lot of good options out there; I reckon the Alienware, MSI and the ugly looking one, Eros or something..., are all good options.