Great article so far!
A few grammar tidbits:
Is there a worse nightmare than having 3 of your kids.....
I would write 'Could there be a worse nightmare'
so they flew on British Airways via London on the outbound journey and on Iberia via Madrid on the return.
I would write 'so they flew British Airways with a stopover in London, and returned with Iberia Airlines with a stop in Madrid.'
Their grandfather accompanied them to the Iberia check-in counter in Miami
-> 'In Miami, their grandfather.......'
but despite asking for the Iberia boarding passes
-> '. When they asked for the Iberia boarding passes.....'
Iberia stranded 3 kids in a city where they didn’t speak the language without taking any sort of responsibility for their well-being.
I would put a comma before 'language'