Many people are 'fired' by their early enthusiasm to develop this into a subsequent career.
We hear of people who sat in an aircraft when very young and this lead to them becoming a pilot later on.
GNE (and other operators) will always need drivers (at least until we get buses that drive themselves), so it makes sense to encourage youngsters - though not to the extent that the day turns into a free-for all for kids.
Polite recognition of the interest shown by those as yet too young to drive (a bus) would be my approach, but not preventing any genuine interest from would-be drivers who are old enough.
You can hold a Passenger-Carrying Vehicle (PCV) licence to drive a bus at the age of 18. At Arriva we tend to select people to train as bus drivers who are 21 or older, and who have held a car driver's licence for at least 12 months. In London, where the driving environment is more challenging, we ask for 2 years experience.
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