Conditions that cause dizziness
Most sessions typically take place while seated which should help out dramatically with children that experience dizziness for various reasons. Still it might be advisable to game in an environment that the child has ready access to a comfortable place they could lie down. This will help in multiple recommended responses to an attack that might cause dizziness.
If you’re so inclined, and the conditions are caused by something like Vertigo, look into information on any or all of the 4 response maneuvers, including Epley, Sermont, Foster or Brandt-Daroff maneuvers.