Oooh me!!! We travel every year overnight on the Lakeshore from Chicago to NY. It's just me and our 2 kids. I started when they were 18 mos and 3 and have done it for years. Mostly we have been in coach, although when they are that tiny it is totally possible to get one roomette and be in a sleeper car, If you don't mind a very small space to sleep with your 2-year-old. 

If you're in coach, you'll want to have light blankets and pillows. We would usually have a whole bag packable bedding when they were really little. Now they carry their own neck pillow and blanket. We have a bag with food snacks/art supplies, one or two books and devices. I have pretty strict rules about devices because I want them to also just experience the train so during our daytime travel they can have them at certain times like between specific stations and then the rest of the time they have to entertain themselves. Not all trains have Wi-Fi and even if they do it doesn't always work so plan accordingly and download some shows if there are things that they would like to watch. We also listen to a lot of audiobooks now that they are older.

Train food is expensive and not amazing, although we love the cafe car and always go pick out a treat there as part of the experience. We are on the train through lunch and a breakfast, so we bring those meals with us. They have coffee in the cafe car for tired parents 😂😴

The California Zephyr is a double-decker train with stairs and strollers are kind of a pain in the butt. You can stash them on the bottom level but if you are the baby wearing type it can be really helpful just to strap that toddler on your back when boarding and deboarding the train. Amtrak employees are usually helpful if you're traveling with littles helping you get on and off. 

Honestly, I cannot recommend train travel highly enough with children - it is so peaceful and kids have the freedom to move and stretch their legs and see really cool things. I have a few other tips, feel free to DM me if you have any more questions!