I hope you reed this before you go...I 45. Stop in the Spring area for a break,
Starting at about Spring and south to a little beyond Beltway 8 is a VERY dangerous area. More murders and other crimes around there than most anywhere else in the Houston area. I call that area along I 45 the murder corridor. A rest stop in the Woodlands (before the I 45 "murder corridor") should be safer.
Have a nice ride and good luck,