Hi!
  I'm really interested in teaching English to older learners. Are the teenagers or kids better and quicker learners, than elderly people? We may never know. It depends on person, I think, but it's nice, when older people are not afraid of learning smth new. I've found an interesting presentation, devoted to this topic here, and some useful tips here. It's never late to study! As Michelangelo said: " I'm still learning".