We attended the Thomas the Train event at Boone Railway. My daughter loved it. They had photo ops with Sir Topham Hatt and Thomas. The ticket included a 20 minute ride on Thomas. They also had model trains set up tp play with. Just don't give in and buy the train set in the gift tent. You can get it much cheaper elsewhere.
Little train buffs will enjoy riding on a real train, but the 2-hour ride was a little long for our younger ones. If you have older kids, this is a fun trip, and there are special kid-friendly trains like the Easter Bunny Express and Thomas events offered during the year. In the summer, there's also a short trolley ride that runs downtown if you don't want to do the big train ride.