I'm beggining to figure out that oltheimmer really knows the good Houston places. Can't go wrong with Williams. But I disagree with the "touristy" claim for Goode Co. Where exactly are all these tourists in Houston? I didn't realize Houston made it into the US tourist destination rotation.
Go to Goode Co. It's in a convenient location to where you'll be located, and has great brisket, sides, and sauce. Also check out Goode Co Seafood. Both places are understandably packed.
Magnolia has the best boiled crawfish in town. It's not in season in Sept, and is far away from where you'll be staying. As is Williams.
I'd avoid Houston BBQ Co and the Luling clone. Those two are trying to do central TX cue. Might as well enjoy the southeast Texas bbq while you're here. When you're in Austin area, search for the Lockhart joints, and go with the those. Everyone wins.
I'll throw Drexlers BBQ in the mix, mostly because it is very close to downtown. Apparently their ribs are excellent. I've never been; just putting it out there.
A small note on the Houston restaurant websites: b4ueat and citysearch are well known, and as a result, of dubious quality. Check out houstonpress.com and chron.com for their recommendations. Both staff reviewers have a special place in their hearts for common man food. Of course, this site is also excellent and the overall recommendations are solid.
You can't leave Houston without some good Mexican food, but that's for another thread...
I'll leave you with some words on Houston: I've had tons of people visit me, mostly for small amounts of time. Most don't get it. I admit, the city didn't make much sense to me when I first moved here as well. Flying roaches, concrete as far as the eye can see, humidity that will strip your wallpaper by itself... But it is a city that reveals its charms after a while. I mention this because your last post mentioned something about depending on transportation options. I'm visioning a skins fan cursing our laughable public transportation.
Another warning: last year, the Texans tried to get homefield advantage by leaving the roof open in Sept. Well, that didn't work out so well.... BUT If that's the case, drink LOTS and LOTS of water.
Have fun!