The hazard doesn't go away due to non-immediate proximity to the vector(s).
COVID19 transmission is primarily via aerisolization, so in your example of 5 members of a family in a gondy cab, let's say only Father has the virus. When they exit the cabin viral particulate will still remain in the air for the next group who enters. What's the average interior gondy size? I'll use Stowe as an example and say maybe 25 feet, give or take. That's really, really, tight for 4 or 6 bodies.
In that tight an environment with no ventilation & low humidity, based on known indoor contact tracing multiple-person spreading examples we have in conditions which are far less "dangerous" than a gondy, I'd speculate almost everyone in that next cabin would contract COVID19. Bonus "contagion points" if Dad's a bit winded from a tough mogul run.
How about taking out all the windows in the gondola? You've got four small windows on the front and back and two larger ones on the door. Maybe leave the doors open on the return trip to air out the gondola?