Admission is $7 for adults, $5 for kids ages 6-16, seniors are $6, and under 6 is free. Hours are 9am-7pm in the summer and 10am-5pm in the winter.
The bottom floor has some displays, but just a couple rooms' worth. It's not a museum or anything.
If your kids love trains, it will be a real treat. I'm surprised you can't see this place from space, it's so big.
For the kiddos they have interactive touch screens where they can color a picture. Can't print it out or anything, though.
Next to the parking lot is also a train car, but you can't climb on it very much.
North Platte is large enough for a couple hotels and restaurants beyond fast food.
Nearby attraction is Buffalo Bill Cody State Park, which also has camping.