Their reasoning seems to be "Well we tried taking them to the local fields but they say nobody under 18 years". Well then, drive little Timmy and his friends way out in the woods if you absolutely have to, and get a permit or something equivalent so they can play safely away from the public.
Also, most fields I've been to is totally fine with kids under 18, as long as there is parental supervision. I think the parents just don't want to pay field-fees or something and would rather let the kids run around the neighbourhood for free instead.
"World's laziest sniper"