We took our son last year and he had a fantastic time, so much so that we are going again this year. This time though, we bought our tickets early so we could get on the first train trip. You may wish to try to purchase tickets ahead of time so you know what time your trip will be; at this late in the game it is highly probable that you will only be able to purchase mid-day or afternoon tickets and I'd hate for you to show up at 9:00 only to have to wait.
Sir Topham Hatt walks around, there was a fire engine with a firefighter (the kids could climb up in it and sit in the driver's seat), there was a Lego Thomas display, a bouncehouse, and a little play area. Also, if your child is interested in trains, the museum (a bunch of big sheds/houses) that have old and I mean OLD el-cars, etc.
The ride itself *is* short but keep in mind that it's for the experience of saying "Mommy - I rode on Thomas the train!", not to take a big trip anywhere (that's what the Metra is for LOL).
Yes, it is expensive, but our son just about lost his mind with excitement and joy so for us it was totally worth it and this is exactly why we're going again this year.