I that vein, a great activity for you! My toddler and I just recently found out about the Day Out With Thomas event in Grapevine. He has just started to get obsessed with trains and cars, anything with wheels, not necesarily Thomas, but i figured it'd be a fun day out.
If you've never been, because apparently it has been around for years, it is so worth the ticket price. We actually took a train ride on a full size Thomas replica and had our picture taken with Thomas and met Sir Topham Hatt. the ride was hilarious and just enough time to not get antsy. They also had all sorts of activities for the kids, music and puppet shows in this outdoor tented area. My son was in heaven.
A friend told me about a cool disount if you purchase tix in advance at http://www.dallasrailwaymuseum.com. use the code MOM in the access field when you check out and get up to 10 tix for $14 each, it a nice discount and well worth the trip. The event runs this weekend as well fri, sat and sunday.
Anyway i thought id share the link as the event is still going on for this weekend, check it out!