From sore experience..!
He should be absolutely fine to fly. In July I managed a displaced compound fracture (clean snap) of the wrist (radius) knocking around with a football - I actually stupidly tried a bicycle kick, which the doctors found hilarious. That was exactly 14 days before flying to the Costa del Sol. I then needed an operation to screw the arm back together, which I received exactly 7 days before flying. That was general anaesthetic and an overnighter in hospital.
Despite all that, I just had to call into the GP a couple of days after my op to check my temperature, the practice nurse removed the bandage from my arm and I put on a velcro splint with a piece of metal in it.
Upshot is, with any luck, even if it is a pretty serious break (fingers crossed it's not) he should be OK for holidays/travelling.