Reddit reviews Bondhus 69499 Ball End L-Wrench Set w/ColorGuard Finish, 9 Piece

These sick colored hex keys. I've worked as a bike mechanic and we used the black version so I can personally vouch for the quality being pretty good.
https://www.amazon.com/gp/aw/d/B00FBFI53S/ref=ox_sc_act_image_4?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

Well definitely get this as you'll never regret having a nice set of hex keys and every fixed gear owner needs a Lockring Tool.

Grease and chain oil are also missing from that set and mission critical if you don't already have them.

For the crankset that kit should have you covered

To go along with the allen keys that you will definitely need I highly recommend some Bondhus Allen Keys. A lot of people on the internet like them a lot, especially for cycling needs.

There's the colored set I linked and also a silver/gold/black set. Really high quality and relatively cheap. I think individual keys are much more handy when working with a bike. There's a imperial set on Amazon too, most bike happen to be in metric though and that's what I linked.

Like /u/jrm2191 said, Park Tool make some... comprehensive tool sets. Those prices are enough to make me choke, though. Your son's riding a ~$400 bike - I don't know how I would wrap my head around buying an $800 tool set, or even a $300 one.

But the tool sets are a good way to think about what tools you should buy. I'd get a basic tool set, fill in gaps, and upgrade selectively. What I'd do, in no particular order, would look like...

• cheap tool set ($40) (total $40)
  
• torque wrench ($50) (total $90)
  
• chain cleaning tool ($10) (total $100)
  
• cable cutting tool ($35) (total $135)
  
• maybe chain pliers? ($10) (total $145)
  
  At this point I would start thinking about upgrading the tools that your son will use all the time. The thing that stands out for me is hex tools. He might use Torx screws, but he'll definitely use metric hex tools
  
  
• some nice metric hex tools ($15) (total $160)
  
• some torx equivalents ($11) (total $171)
  
  Then probably nice meaty tire levers to make replacing tires and tubes easier
  
  
• tire levers ($9) (total $180)
  
  If you were looking to spend $300 or that range, then you'll notice you're way under that target. Feel free to start adding on some random nice things, like a portable multi-tool, which will pay off if he has an issue while out on a ride.
  
  
• Portable multi-tool ($25) (total $210)
  
  I'm running out of things that aren't "consumable" (like brake cables, housing, etc...), so for my last recommendation, nitrile work gloves! (they'll make cleanup a breeze)
  
  
• work gloves ($20) (total $230)
  
  There are tons of other things you could get (a bike stand, for instance) but at this point I'm getting a bit out of control. and there are tools I assume you have (e.g. a good screwdriver), but at some point I need to stop.
  
  And obviously feel free to mix and match whatever components you can afford/feel comfortable spending that much money on. One thing that might help would be to talk with him about what kind of work he does on his bike. He might be in desperate need of hex tools, but not treating himself to nice hex wrenches. That could be your quick, easy, cheap answer. Or similarly he might be nervously tightening bolts without a torque wrench, even in places that call for very precise amounts of torque. Again, easy answer regarding what to prioritize.
  
  Best of luck
  
  edit: totals didn't add up right, sorry!