I did this trip last year (Chicago to Houston) and I planned it out similarly to what you're doing now.

I have 2004 330xi and got new tires, as well as every repair my mechanic could find. I told him that we were planning a road trip and to fix everything! He actually found a crack in the water pump that could have been disastrous had it failed somewhere in the middle of nowhere. I also had a jack installed so that we could plug in the ipod.

I think it took us about 19 hours. We stopped in Memphis both ways, and stayed at a funky place called the Talbot Heirs http://www.talbotheirs.com. It was right downtown, in case you want to see Beale Street, eat some BBQ, etc.

We opted to take I-55 to I-10, which seems a little out of the way, but we were driving during a really bad storm and felt that sticking to the major highways was the best plan. If you do this, I highly recommend a stop at Steamboat Bill's in Lake Charles for some fried seafood

It's amazing how much less gas costs in Texas.