Yes, hearing aids should be included.
It is recommended to keep any electronic devices away from an operating Van de Graaff generator because the sparks produced (even if only small) can damage the electronic circuits. This applies to anything that has an electronic chip or circuit board including: cell phones, cameras, watches, computers, hearing aids and USB storage devices.
In addition to the risk of damage to the hearing aid itself, there is also the risk of the hearing aid emitting a high-intensity noise if used near a running Van de Graaff generator. This could result in hearing damage.
Lamont James. Technical Officer– Electrical Engineering, Deakin University. February 2016. Personal communication
‘Van de Graaff generator safety’ Institute of Physics website, http://practicalphysics.org/van-de-graaff-generator-safety.html (Accessed February 2016)
‘Van de Graaff Generator Safety’ Storm Highway website, http://stormhighway.com/graaffsafety.php (Accessed February 2016)