I’ve done lots of this lately as mine is car sick. We have it down to a fine art.
No way I can collapse a pram laden with stuff, so we get on at the wheelchair or bike doors. I’m now familiar with most of the types of train and can tell which area will be best and have most room away from other people!
Most wheelchair areas have space for two chairs or prams, and are near the accessible toilet. I push the whole pram into the toilet if necessary. If toddler is out of pram and wearing shoes (hit and miss) I leave pram and take him on foot, but he likes to bash at the bright red emergency buttons which are at toddler height. Guard those with your life when peeing.
Get pram on and off backwards as much easier. Call for help of guard if gap is huge.
Take more small snacks than you would ever normally allow. Like, a bag full.
Take new books or toys. Mine likes lift the flap so I get new ones for the journey.
Hate to say it but mine rarely sleeps. Too much excitement out of routine. We power through if necessary. Mine still breastfeeds so I have to balance shouts of “BOOBIE!” with flashing my boobs to a whole carriage.
Weirdly, I’ve always enjoyed our train journeys because we can snuggle and bond (over snacks…). It’s hard when he refuses to go back in the pram or wants to maraud around the carriage with no shoes on, but yours might be less energetic….
Tip: don’t be afraid to abandon your booked seat if the train isn’t busy to find a quieter carriage. Rush hour can be much more stressful. Don’t get on with a buggy and expect it to fit in the normal luggage rack or to push it down the aisles. Tactical carriage choice is key.
Keep checking the train line app as ALL my recent journeys had last minute cancellations. You have to be ready to go with the flow, even if it means waiting for a while in random stations for the next valid connection.
Again. More snacks than you think is feasible. Good luck!