Traffic in Houston on Friday is ALWAYS a problem, especially after mid day.
If you get to Houston on Friday, I would suggest that you get off I-10 going west just after the Channelview/Baytown area, and take Beltway 8 north. It will loop around the city and reconnect with I-10 on the west side of Houston bypassing most of the traffic congestion. It is a toll road though.
If you get to Houston on Saturday or Sunday you shouldn't have any problems at all just taking I-10 straight through.
Best of luck and happy camping!