Following up: It may not have been a good idea, but we did it anyway!

AWESOME!

Of course it was a good idea... look at those smiles!

The rest of this post will be for future travelers, since I am far too late to this party. I was in the middle of my own trip where we brought a bunch of games that met your criteria. Our kids are 12 and 14 years old. We packed games for our flights between California and Europe, for a couple of hours on a TGV train, and for whatever downtime we had in the weeks that we were over there.

* Playable by 2-4 people, including kids ages 7-13.
* Easily portable, and won't take up too much space in my carry-on bag.
* Playable on a small table on a moving train....

For us, our games really needed to be portable, because were traveling with only carry-on bags. No checked bags. We had enough table space on our airplanes, and even more on our train ride (pictured). On the left of this photo you'll see our main game box (...a durable, re-purposed Smash Up expansion box) that held 5 or 6 card-based games.

http://postmyimage.com/img2/547_20190712_070315.jpg

Port Royal (pictured)
Illusion
Math Fluxx
Tides of Time
The Game
Love Letter
Fuse
Railroad Ink
Happy Salmon

All of these games are light, and enough of them can be played with just 2 players. We're on vacation! There is one more game that I am forgetting now (Coloretto? or No Thanks?) because we never actually played it. We brought 10 games total.

My list is nothing special. So many games would work. A regular deck of cards. Obviously, card games are more portable than board games.

My suggestion for all travelers is to playtest your games before your trip. A bigger game that you will definitely play is better many smaller games that you won't play. Some other brand new games didn't make our cut (Arboretum, NMBR9) because my kids weren't crazy about them.

Fitting your theme, Railroad Ink would have been a way more manageable train game than Ticket to Ride. OR, you could have just gone with the digital app instead. ;-)

--Rod