How to plan trip to the HMNS?

Hey guys, this April I'm traveling to Texas with my boyfriend and his family. We will only have one day in Houston and we really want to go to the Houston Museum of Natural Science. Since we only have the one day, I was wondering if anybody had any recommendations on what order to see things in, when to book the tickets for certain exhibits, etc. I am also wondering about the food that the museum has. Is it overpriced, does it taste ok? Can we leave and return for lunch? We don't travel too much but I really want to see all that I can so if anybody could help I would greatly appreciate it!!