I bring a power strip to plug in all the electronics. I have a couple packages of cheese crackers for the unexpected, a bottle of water per person, also just in case. A camera is a must, the scenery on both sides of the train is spectacular. I bring headphones so I can listen to music and a book to read during long stops,if they occur. At night I like to open the curtain to watch the stars and the small towns pass by. I bring my own toiletries for taking a shower and getting cleaned up each morning. If you like hot tea, i bring a selection of tea bags, then get hot water either in the Dining Car or the Lounge. I also have an insulated cup to keep the tea hot longer (or coffee in the morning). I bring our GPS to keep up where we are and how fast we are going. My granddaughters really enjoy watching the speed. I have a backpack with everything I will need in the room, so I can leave the roller bag on the shelf down stairs. FYI- If traveling with teen girls, like my grand daughters, they require over twice the luggage space you have planned for. I also carry, stretchy straps in case I need to secure something in place, maybe the backpack, etc. I always have a screw driver. small pliers, small roll duct tape, also a small high power flash light. Have your medications labeled and easily accessible, like in a pouch in the backpack.
Hope this helps. I am a planner, so I always make a list divided into where I plan to place the items.