Reddit mentions of Park Tool CN-10 Professional Bicycle Cable and Housing Cutter

First off, the brake levers you have are probably not compatible with V-brakes. V-brakes need special long pull levers. Try looking for cantilever brakes instead. They'll look sort of like the ones you already have.

Besides that, to install brakes, you'll need some hex keys, a cable cutter, and some new cables. Park tool's website should have a guide, or search youtube for installing cantilever brakes.

You can't go wrong with the Park CN-10.

For years I just used a pair of linesman pliers, hitting it with a mallet would usually get me a good clean cut. Housings I'd just hacksaw or Dremel.

Once I picked up the Park, it was like "Holy shit".

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!

If you can afford that S3, you can afford some decent tools:

cable stretcher

cable cutter

If you shop around, both can be had for about $25 each during sales. Well worth it considering an LBS visit is usually more than $50.

And just to double-check because the pads aren't of the vibrant color variety, but be sure that the pads used on the Zipps are not the pads from use with alloy braking surfaces. Carbon requires a special brake pad.