K.F.
Not sure when your company is visiting (sounds like maybe sooner than this), but the last weekend in March and first weekend in April, they have the "Day Out with Thomas" at the Grapevine Vintage Railroad ( http://www.grapevinesteamrailroad.com/events.asp )where they have a "Thomas" engine pulling the train. We went last year with our then two year old and he loved it. There are lots of activities besides the train ride- miniature trains on display, trains for the kids to play with, get your picture made with Sir Topham Hat, etc. Even if it's not the weekend that Thomas is there, the regular train ride might be a lot of fun. Hope you have a nice visit with your family!
:-) K.