No, I don't think it is a mistake. It's not like you need the warmth of a fireplace in Texas. You'll enjoy the fire when you want, and you won't have to worry where to put the TV in the family room if there isn't a fireplace. One fireplace is enough...for me, anyway. :)

Depends on if you like fire places. If I was building a house that big I'd want them everywhere, but it's a personal decision.