We just finished a couple night stay at the Westin Stonebriar with our family. The hotel is nice, but I would recommend another place for people traveling with families.
The rooms are fine, but like many others here I did not receive any consideration for an improved room with SPG Platinum status. Therefore, you are likely to be sleeping in a two bedroom regular hotel room, which is fine (and what I paid for), but I have grown accustomed with my status for a little better treatment.
The pool area is relatively small - our children (11 and 14) were both bored fairly quickly. It feels like it is made more for adults to lounge around the pool vs. an active family. There is no SPG floor and therefore no SPG amenities. We found ourselves going to the nearby (10 minute drive) Legacy Mall for Starbucks and dinner. Plus you are a long way from central Dallas and some of the activities there (with a lot of traffic).
Therefore, in summary, a nice and clean place and a quiet location, just lacks character and caters to conferences/business travelers with very little to offer families. I will be staying elsewhere when I return to Dallas.