great to get kids out doors into the bush. Be great to see the brag photos.  Good luck 

Be it a long bow or Cross, it is no different to a rifle except more so
 The ability to drop that bolt/ arrow exactly on the spot for the kill. If dont yo have a very long, and if a goat , very challenging (clifts, gullies) hike to chase it down.

The bow, to be able to pull it fully AND shoot accurate over distance is not for the inexperienced...and a cross bow much the same.

I looked into it yrs ago, talked with a few ppl and couple bow hunters...these guys tend to progress from good very experienced gun, stealth hunters to bows.
 Not drop straight into a 'bow...and the usual reason for young guys is to short cut the process of getting a gun license, and the cost of a suitable gun (generally over the $1200 mark.. plus setting up secure storage.

1 of our sons went thru this 'phase' around the same age...
He did his homework with a bit of proding... a couple friends dads having an informal chat..
He eventually went sat his firearms licince, got his 1st 7mm, and hooked up with a couple good hunters.

For good bow hunting you need to be a very, very good stalker.

 Disagree...
 to get anything at all, "you need to be a very very good stalker" , and excellent bow person and experienced hunter/ bush man.

unless walking the Ohatu drains for koi, and that takes a just bit of practice.

I recommend ScorpydAculeus with 460 fps for hunting because It is very fast in speed and really convenient to use and work with. The weight of this crossbow is not so light but comparatively, it is not that bad.