I am sorry your dogs suffered heat stroke but glad that someone was there the help you out in getting him back to the car.  You are so right that heat stroke is a serious matter especially in the south - I expect Texas to get really hot this summer.  Anyway, one thing that really helps to beat the heat wherever you are is wind (moving air) and water.. so please check out those misting fans. They worked great for me and my Caucasians in Texas.  You can also consider those misting hoses that you hang.  Anyway, here are two that works.

I used this one and can attest to its value.

This one also looks great but it does not oscillate

http://www.amazon.com/Lasko-7050-Misto-Outdoor-Misting/dp/B0073CQ9CQ

Try this link for the misting hose that hangs on your patio or other place to provide a cooling mist.

http://www.amazon.com/MistyMate-16020-Patio-Outdoor-Misting/dp/B001EJHTAA