Twice, once short-haul, once medium-haul.
The vet recommended that the puppy was sedated although we weren't keen as I was handing it over to its new owners at LHR. We gave the puppy its pill and it was then checked in as luggage.
At LHR the puppy was right as rain having spat the pill out when we were not looking.
The other was a 90lb German Shepherd - different league to your small dogs. It required an huge crate in which it could stand up, turn around or lie down. Lying down required a floor plan of 5 feet by 3 feet. Total time in the crate was about 9-10 hours allowing for handling - no sedation.
You need to find out whether you need one crate per dog and the size of the crate(s). You should introduce your dogs to the crates up to 4 weeks before the flight. Put their food in the crate, put their bedding in the crate in the same room in which they normally sleep. Gradually increase their time in the crate with the door closed.
They will soon accept the crate and be less stressed on the flight.