White Rock Lake sounds doable and safe at night. I often ride with the Night Riders group in Ft. Worth (Doohickie introduced me to them), and I think there is a group like that in Dallas as well. I've really been enjoying riding at night. In the summer it lets me stay away from the energy draining heat and when it gets dark early, I am not limited by the short day.

For headlights, I have a 200 lumen Cygolight, which is a dedicated bicycle light. I also have a 200 lumen Coast PX-25 flashlight ($40 at Home Depot, + a flashlight holder)up front as well. The two beam patterns combine nicely and light up the road ahead of me very well. Two lights also gives me some redundancy in case one runs out of power on a ride.

In the back I am using a Planet bike superflash in blinking mode on the bike and I recently added a smaller light on my camelbak that i leave in steady mode.