I recently took my 11-year-old daughter and her friend on a day trip from BWI to New York City and back on the Northeast Regional. The trains were quite crowded in both directions.
On the way up, a kind passenger offered to switch seats so the girls could sit together, and another person moved so I could sit nearby. On the return trip, other passengers also offered their seats, allowing the girls to sit together comfortably.
Both trips were made much better by the helpful and friendly people we encountered. Even though the train was full, the positive interactions made the journey enjoyable, and the girls really loved the experience.