Other children might scamper through the airport, delighted by the moving sidewalks and dreaming of sand castles. But for Ms. Napoleon’s son, the crush of unfamiliar faces, the creeping pace of security lines and delays in boarding and takeoff can trigger excruciating anxiety.

So before flights Ms. Napoleon worries: Will he dash through the metal detector without stopping? Will he disrupt other passengers by kicking the seat incessantly? Will he have a meltdown onboard, screaming and crying and hitting himself in the head, and get the entire family forced off the flight?

Her son, Keanu, is autistic. So for the Napoleons — and many other parents of children with autism — family vacations can be an agonizing exercise in parental endurance.