My sister told me about a man in Richardson who set up a train in his backyard and opens it nightly during the holiday season for anyone and everyone to come ride. It's pretty amazing to see in person, and if you've got little ones, you should definitely stop by! They run the train every night from 6-10pm, between Thanksgiving and New Years. I recommend you go on a weekday night because there will be less people there. We visited tonight, and it was so much fun! They don't charge anything to ride, but you can certainly make a donation to help offset their operating costs, if you feel so inclined. It's a fun family activity, and your kids will love it! You should check it out. Here's more info.
Train that goes around a large display of lights and holiday characters
Dutch's first train ride - trying to take it all in!
My niece and I having a blast on the train
And here's a video of it to give you a better idea: