It's open to kids six and older for these dates: June 18, July 16 and August 13, 2010. Kids need an adult chaperone (at least one adult per five kids). It goes without saying (though I'll say it anyway), adults need to come with a kid. No solo adults!
The event includes: "Overnight immersion in the wonders of science and animal life," sleeping in the rainforest or aquarium exhibit, watching a show in the planetarium, an evening snack, breakfast, and a commemorative gift, and free parking below the museum.