We frequently fly long-haul on an 11 hour overnight to visit DH's parents in South Africa. Father in law is unwell so we do it fairly often...
Seeing as they have to sleep in these really-uncomfortable-looking chair things, and there are all kinds of bangings and crashings coming from the galley (which is invariably next to the bulkhead) people to-ing and fro-ing and banging into said chair, etc etc. I've always given DD a smallish dose of Medised/Calpol Night (same stuff, different label) after take-off (again, I know it works for her as she's had it from time to time when suffereing with coughs and colds).
While it hasn't exactly been an unbroken night's sleep (you keep having to taken 'em out and buckling them to you when there's turbulence) it has, at least, been peaceful and untraumatic.
Last time we sat next to a woman travelling by herself with an 18 month old and a 2 1/2 year old who screamed/cried/wailed almost constantly for eleven hours.
While not wanting to be a 'pusher' I did offer her some of my Medised after about 4 hours (because, frankly, the only one getting ANY sleep for a 10 yard radius of her DCs was my DD and they both were in such a state.) She looked at me like I was a crack dealer and said, dead snootily "no thanks, I don't believe in drugs unless they're ill.."
Which is fair enough, I suppose, but they both looked pretty wretched/ill the next morning after 11 hours of screaming...
So, yes, I "drug" my daughter on long-hauls, and don't feel remotely guilty about it. She wakes up feeling refreshed and able to cope with the rest of the journey, and everyone has a more pleasant flight - including any unfortunates who happen to be sitting next to us.
Why not take some along, just in case? You don't have to use it unless they get distressed, in which case it can't hurt to have a plan b.
They might be perfectly fine on the flight... but on the other hand... ??
db
xx