V.P.
Welcome to Texas! I know that it's probably been a roller-coaster of emotions. Having lived in Chicago all my life, when I moved to Texas 17 years ago, I was exited and nervous. I would definitely encourage you to find a playgroup, mom's network, etc. It will provide wonderful support for you and your family. Even after living here for 7 years, once I had children and stayed home with my kids, I needed to make another whole circle of friends.
As for where to move, you have lots of wonderful options in Texas, and the cities you're looking at are great. When we moved here, we also lived in corp housing in Irving (Las Colinas) while looking for a house. We bought in Flower Mound and have loved it ever since. It's a wonderful family community, and has excellent schools. To learn a little bit more about what this area has to offer, I would encourage you to take a look at a few issues of Family eGuide www.familyeguide.com. We feature family activities in the Flower Mound, Lewisville and Highland Village area. We have a new website launching in about 2 weeks, which will also give you an extensive calendar of events, and comprehensive resource list of family-friendly businesses.
Good luck! Based on your choices, you really can't go wrong.