I've witnessed spontaneous combustion. It occurs when I unite my 10-year-old daughter with her two precocious cousins, ages 10 and 13. Putting these girls together is like putting a lighted match to gunpowder. An explosion of screeching, shouting, jumping and caterwauling follows. When planning a summer trip with my daughter to the San Francisco Bay Area to visit my nieces, I had scores of choices for educational diversions -- museums, aquariums and art exhibits. But kids with this kind of energy need some frivolous fun to balance the mental stimulation. So, my plan was to pair the cerebral stimulus of a visit to the recently opened California Academy of Sciences in Golden Gate Park with the lighthearted fun of a stop at the Burlingame Museum of Pez Memorabilia, which bills itself as the world's largest tribute to Pezdom. As tributes go, it's a bit modest. The Pez museum is no bigger than a corner convenience store, while the science museum stretches over more than 400,000 square feet of environmentally friendly exhibits. And yet the girls enjoyed both attractions almost equally. That's no surprise to any parent who has spent a fortune on a Christmas present only to find the kid fascinated by the box that held the gift. First, some money-saving tips: The California Academy of Sciences offers free admission on the third Wednesday of every month. (The usual fee is $24.95 for adults, less for teens and children.) But on free Wednesdays, arrive early because the lines are monstrous. Also, pack a lunch and eat it at the outdoor terrace because food prices in the museum restaurants are also monstrous. Second, you can avoid driving to the Pez museum by taking the Caltrain to the Burlingame Avenue station, about a block from the museum. Admission is $3 for adults, $1 for children ages 4 to 12. When we pulled into Golden Gate Park, a line snaked all the way to the entrance of the California Academy of Sciences. Still, it moved quickly, and we were inside about 15 minutes after the doors opened at 10 a.m. The museum includes a planetarium, an aquarium and many other exhibits, but the main attraction is definitely 'Rainforests of the World.' We climbed a circular walkway that spirals around the inside of a 90-foot-tall glass dome and looked down at a pond, teeming with fish, bordered by trees full of birds. The humid, warm air fluttered with butterflies of amber, crimson, brown and black. 'This can't be real,' my daughter, Isabella, said as she eyed a 20-foot python in the exhibit. But everything in the exhibit -- including the bagel-sized Borneo river toad and the strawberry poison dart frogs -- was very real. The museum has already drawn more than 1.6 million visitors since it opened in September 2008. At the end, the girls gave the museum high marks, saying it was much more enthralling than they had expected. 'I thought it was just going to be statues that you look at,' said my niece Amanda, 13. No, the motionless figurines were at the Pez museum. What is billed as the largest collection of Pez memorabilia in the world resides in a former computer store, sandwiched between a rug-cleaning business and a music shop in Burlingame, a town about 15 miles south of San Francisco. Gary Doss, the founder of this quirky joint, was on hand to recount the history of Pez. The candy was invented in 1927 in Austria, he said, to freshen the breath of smokers. So, the first Pez dispenser was designed to look like a cigarette lighter. The dispensers eventually evolved to attract kids, with the addition of faces such as those of Santa Claus, the Smurfs and Chicken Little, among others. The Pez museum has one of every variety of dispenser ever made, or about 750 versions, according to Doss. The rarest: a Mr. Potato Head-type dispenser with tiny removable parts. It was recalled because of a potential choking hazard, so it's hard to find, he said. But that was not enough for Doss. He and some buddies also built the world's largest Pez dispenser, a giant snowman that stands 7 feet tall. The girls seemed unimpressed. The dispensers were cute and all, but visitors are not allowed to touch or play with the museum exhibits -- a real bummer for energetic kids. But the girls were able to handle -- and take home -- dozens of dispensers at the adjacent Pez store, for a price. (The prices range from $2 and up, depending on the age and model.) That's where the girls became animated. Their big eyes scanned the shelves of toys. 'I want them all,' Isabella cried. In the car ride back, the girls munched on Pez candies and played games with their dispensers. (I limited each girl to two dispensers.) My 10-year-old niece Micah dubbed it 'cool, because we bought candy.' The girls agreed that the Academy of Sciences was their favorite stop. At the end, they said, the fluttering butterflies edged out the Pez candies, but only by the slimmest margin. 