No one does. Seek out a staff member - they're often called demonstrators or explainers. Respect your children's ideas. Enjoy their perceptions of what they see, hear, and feel. Their experience is more limited than yours, and some of their ideas may seem na ve or puzzling.
Scientific breakthroughs start when somebody sees the world in a different way.
Take in a movie. Go see one if they're available and you'll get to sit down, too. Large-screen films are best for ages 5 and up. During holidays, it may be wise to buy tickets for special shows in advance. Science centers are for kids - and adults.