True! About what suits your natural rhythm the best. Always had a longish runup myself, but each young bowler needs to decide that for himself. I do not take kindly to a coach interfering with a bowler's natural runup.
Run-ups. Gah. If I had a cookie for every time I'd seen a kid charge in from 20 yards and then stop dead in his tracks before slinging down a tasty slice of pie...
Reckon the key here is how honest the batsman is -
That's not the run-up's fault
Have seen the same thing actually, such a waste of energy. 
Which is the actual reason that I think bowlers have very long run ups. It is easier to control your body if you're not accelerating at a particularly fast rate. At the same time, bowlers do not want to steadily jog in off 5 paces because they won't be going very fast. So they compromise and run in off a long run.
Feared fast bowler at 16 bowling around 110-115kph sounds right to me.
The ordinary school does not have multiple players at county standard.
It's quite relative, in my modest understanding. Cooch-Behar, club cricket (very much dependant on which club we're talking about), U-19 and U-22 are all vastly different leagues and as you'd appreciate, the average batsman's comfort level against pace would be different.
Yeah agreed 110kph might not trouble bats of a higher standard, but point being there might not be a lot of kids bowling much quicker than that, and probably tends to zero 17 yo 140 kph merchants like Aamir, Lee etc. -)
I think it's incredibly rare to get someone in their teens bowling exceptionally quick for their age. You generally have to be built a bit like an adult (i.e taller than average and stockier as well). I'm betting the 10 year old is more physically advanced than other blokes his age.