Coach, particularly over the holidays, is all ages. Lots of college students, retirees, people going to football games. Families with little kids. Card players and guitar players in the cafe. Amish couples. Foreign students or teachers on holiday. (Sleepers are more expensive, so you get an older crowd plus a few families.)
All ages ride Amtrak now days. I am a frequent rider on Amtrak and have met a lot of people. From Babies to the grandparents are riding on the train. Yes you will meet some very nice people and have a great talk about a lot of stuff. You will enjoy it, I do everytime. I love riding the train. Kick back and relax.