Kemah stinks, I'd sooner hit up Galveston and the strand. Hit up Moody Gardens if you like aquariums. The rainforest pyramid stinks though, don't waste your money unless you like staring at plants and two parrots.
Check ahead and see if there are any shows at the House of Blues. Overpriced food/drinks, but still a nice place. There is a comedy club a bit further out west right near the 610/I-10 intersection that's always got shows, and it's right next to a huge IMAX theater also.
Right in the heart of downtown is the Galleria, one of the biggest malls in the US. Everything from your regular stores to your uber-high-end stuff. Ice skating rink downstairs, blah blah blah. About two blocks away from the mall is the giant waterwall monument. Makes for some cool pictures, and a nice refreshing mist to boot.
The museum district isn't bad either. Museum of Natural Science is pretty good, the Modern Art museum stinks, Museum of Fine Arts is pretty good. Check and see if the Art Car museum is open. Definitely some cool stuff in there, and it's off the beaten path as well. Herman Park often does concerts/shows at night and is right across the street from the museum district, so see if anything is going on there as well. The zoo isn't overly impressive either, especially in the heat.
As for the roads in Houston... yikes. Most of I-10 isn't bad, neither is the Beltway, but 610 and most of the regular roads are TERRIBLE.
Space center is cool, both literally and figuratively. In all honesty, spend as much time as you can indoors. People are complaining about how "hot" it is here in NC, and I'm about ready to put on a sweatshirt. Houston is VERY hot and VERY humid, and there is a good reason you don't see many people outdoors in the summer. When nightfall hits is when you see a lot of people out.
BTW, East Houston and South Houston towards Pearland are notoriously bad, that's a given. When you get into the heart of downtown and go further west towards Katy, it's very nice. Take a drive down Memorial and some of the roads out that way, and you will see some VERY high end neighborhoods. I was in West Houston out towards Katy, and the only shooting around there was when someone tried to rob the bank in the middle of the afternoon.
Oh yeah, don't forget to go see the beer can house!
By the way, if you're looking for some adult beverages, check out this hole in the wall called Lola's. It's behind an Autozone, has no sign, and looks like an abandoned building. It is my all time favorite bar. Some very "interesting" people in there, and the cheapest, strongest drinks on the face of the planet. Happy hour goes until 11pm. I spent many a nights in Lola's, and never felt unsafe either.
