Hi Jo!

SNCF do not provide child rails or cots on their sleeper services, whether you travel in couchettes or actual sleepers.

Make sure you specify that you want a lower couchette - they are in 'banks' of 2 or 3 (4 or 6 to a compartment). You might find it worth bringing a pram mattress or travel cot and setting up a bed on the floor for the baby - and/or the toddler. Hopefully your fellow travellers will accept this with good grace!

You will need to bring plenty of water (SNCF supply a small bottle of still mineral water per berth) and child-friendly food and drink. Some quiet toys too will be useful (not rattles or mechanical voice things!!) and PLEASE do not forget the favourite teddy/blanket/dummy! You won't have access to your car en route, so please make sure you've got everything you need before you leave it.

Might you want to discuss with your doctor the possibility of giving your child a mild sedative before travelling?

Perhaps if you were to change the children into pyjamas they would accept the concept of 'going to sleep' a bit better, but make sure that they will be warm enough to carry from the train when you arrive at Narbonne, because the train will be continuing on towards the Spanish border so you'll have to get out of your carriage pronto!