From personal knowledge of the terrain and demographics of the various areas N of downtown Dallas, and of course the following is all IMO....
Bachman Lake is extremely extremely extremely unlikely to be the place where CM is. Like, 1 in a million or less that it would be her. It's just the wrong area to make sense for EA to take a quick-to-medium-length drive and get rid of her, and it's not on the way to anywhere he would otherwise have traveled. He's a suburban kid, living far far N, and far far E, and he's either taking her someplace he sees all the time (in his broad vicinity) or he's going farther N or father W to less inhabited areas. And even more, there are so so so many areas, hundreds of better ones, in between his home and here, that he would have had to go past to get here with her.