I know the ISS speaks to folks on Earth via ham radio - I don't know if those sessions are scheduled in any way, but talking to an Astronaut or Cosmonaut could be a treat for him.
These contacts are occasionally scheduled with organizations (schools etc.), but unscheduled for the general public.
Exchanges tend to also be one short question (how does earth look from above right now?) and one short answer (earth looks beautiful), and then it's on to the next person. Not just due to congestion, but also because the ISS is only visible for a few minutes.