Several times it's mentioned that Ernie is ten years old. This episode aired in January 1967, one month after Barry Livingston's 13th birthday.
They never tell you where Bryant Park is located...but, considering one of Steve's contracts (he's an independent engineer) is the Air Force, possibly on the California border near Area 51 in Nevada. Ernie did actually see (to him) a UFO or Unidentified Aerial Phenomenon..
Remote controlled Air Force secret aerial vehicle, before being called Drones. And, typical government tells him to be quiet about it.
All the boys are actually 3 years older than the characters they portray...